Publications by year
In Press
Rapkin J, Archer CR, Grant CE, Jensen K, House CM, Wilson AJ, hunt J (In Press). Little evidence for intralocus sexual conflict over the optimal intake of nutrients for lifespan and reproduction in the black field cricket Teleogryllus commodus.
Evolution Full text.
Wilson A, Pascoal S, Hunt J, Mendrok M, Bailey NW (In Press). Sexual Selection and Population Divergence II. Divergence in Different Sexual Traits and Signal Modalities in Field Crickets (Teleogryllus oceanicus).
Evolution Full text.
2021
Hampton KJ, Duffield KR, Hunt J, Sakaluk SK, Sadd BM (2021). Male and female genotype and a genotype-by-genotype interaction mediate the effects of mating on cellular but not humoral immunity in female decorated crickets.
Heredity (Edinb),
126(3), 477-490.
Abstract:
Male and female genotype and a genotype-by-genotype interaction mediate the effects of mating on cellular but not humoral immunity in female decorated crickets.
Sexually antagonistic coevolution is predicted to lead to the divergence of male and female genotypes related to the effects of substances transferred by males at mating on female physiology. The outcome of mating should thus depend on the specific combination of mating genotypes. Although mating has been shown to influence female immunity in diverse insect taxa, a male-female genotype-by-genotype effect on female immunity post mating remains largely unexplored. Here, we investigate the effects of mating on female decorated cricket baseline immunity and the potential for a male-genotype-by-female-genotype interaction affecting this response. Females from three distinct genotypic backgrounds were left unmated or singly mated in a fully reciprocal design to males from the same three genotypic backgrounds. Hemocytes and hemocyte microaggregations were quantified for female cellular immunity, and phenoloxidase, involved in melanization, and antibacterial activity for humoral immunity. In this system, female cellular immunity was more reactive to mating, and mating effects were genotype-dependent. Specifically, for hemocytes, a genotype-by-mating status interaction mediated the effect of mating per se, and a significant male-female genotype-by-genotype interaction determined hemocyte depletion post mating. Microaggregations were influenced by the female's genotype or that of her mate. Female humoral immune measures were unaffected, indicating that the propensity for post-mating effects on females is dependent on the component of baseline immunity. The genotype-by-genotype effect on hemocytes supports a role of sexual conflict in post-mating immune suppression, suggesting divergence of male genotypes with respect to modification of female post-mating immunity, and divergence of female genotypes in resistance to these effects.
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House CM, Lewis Z, Sharma MD, Hodgson DJ, Hunt J, Wedell N, Hosken DJ (2021). Sexual selection on the genital lobes of male Drosophila simulans.
Evolution,
75(2), 501-514.
Abstract:
Sexual selection on the genital lobes of male Drosophila simulans.
Sexual selection is thought to be responsible for the rapid divergent evolution of male genitalia with several studies detecting multivariate sexual selection on genital form. However, in most cases, selection is only estimated during a single episode of selection, which provides an incomplete view of net selection on genital traits. Here, we estimate the strength and form of multivariate selection on the genitalia arch of Drosophila simulans when mating occurs in the absence of a competitor and during sperm competition, in both sperm defence and offense roles (i.e. when mating first and last). We found that the strength of sexual selection on the genital arch was strongest during noncompetitive mating and weakest during sperm offense. However, the direction of selection was similar across selection episodes with no evidence for antagonistic selection. Overall, selection was not particularly strong despite genitals clearly evolving rapidly in this species.
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2020
del Castillo E, Chen P, Meyers A, Hunt J, Rapkin J (2020). Confidence regions for the location of response surface optima: the R package OptimaRegion.
Communications in Statistics: Simulation and ComputationAbstract:
Confidence regions for the location of response surface optima: the R package OptimaRegion
Statistical inference on the location of the optima (global maxima or minima) is one of the main goals in the area of Response Surface Methodology, with many applications in engineering and science. While there exist previous methods for computing confidence regions on the location of optima, these are for linear models based on a Normal distribution assumption, and do not address specifically the difficulties associated with guaranteeing global optimality. This paper describes distribution-free methods for the computation of confidence regions on the location of the global optima of response surface models. The methods are based on bootstrapping and Tukey’s data depth, and therefore their performance does not rely on distributional assumptions about the errors affecting the response. An R language implementation, the package OptimaRegion, is described. Both parametric (quadratic and cubic polynomials in up to 5 covariates) and nonparametric models (thin plate splines in 2 covariates) are supported. A coverage analysis is presented demonstrating the quality of the regions found. The package also contains an R implementation of the Gloptipoly algorithm for the global optimization of polynomial responses subject to bounds.
Abstract.
Pascoal S, Risse JE, Zhang X, Blaxter M, Cezard T, Challis RJ, Gharbi K, Hunt J, Kumar S, Langan E, et al (2020). Field cricket genome reveals the footprint of recent, abrupt adaptation in the wild.
EVOLUTION LETTERS,
4(1), 19-33.
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Duffield KR, Hampton KJ, Houslay TM, Rapkin J, Hunt J, Sadd BM, Sakaluk SK (2020). Macronutrient intake and simulated infection threat independently affect life history traits of male decorated crickets.
Ecology and Evolution,
10(20), 11766-11778.
Abstract:
Macronutrient intake and simulated infection threat independently affect life history traits of male decorated crickets
Nutritional geometry has advanced our understanding of how macronutrients (e.g. proteins and carbohydrates) influence the expression of life history traits and their corresponding trade-offs. For example, recent work has revealed that reproduction and immune function in male decorated crickets are optimized at very different protein:carbohydrate (P:C) dietary ratios. However, it is unclear how an individual's macronutrient intake interacts with its perceived infection status to determine investment in reproduction or other key life history traits. Here, we employed a fully factorial design in which calling effort and immune function were quantified for male crickets fed either diets previously demonstrated to maximize calling effort (P:C = 1:8) or immune function (P:C = 5:1), and then administered a treatment from a spectrum of increasing infection cue intensity using heat-killed bacteria. Both diet and a simulated infection threat independently influenced the survival, immunity, and reproductive effort of males. If they called, males increased calling effort at the low infection cue dose, consistent with the terminal investment hypothesis, but interpretation of responses at the higher threat levels was hampered by the differential mortality of males across infection cue and diet treatments. A high protein, low carbohydrate diet severely reduced the health, survival, and overall fitness of male crickets. There was, however, no evidence of an interaction between diet and infection cue dose on calling effort, suggesting that the threshold for terminal investment was not contingent on diet as investigated here.
Abstract.
House C, Tunstall P, Rapkin J, Bale MJ, Gage M, Del Castillo E, Hunt J (2020). Multivariate stabilizing sexual selection and the evolution of male and female genital morphology in the red flour beetle.
Evolution,
74(5), 883-896.
Abstract:
Multivariate stabilizing sexual selection and the evolution of male and female genital morphology in the red flour beetle.
Male genitals are highly divergent in animals with internal fertilization. Most studies attempting to explain this diversity have focused on testing the major hypotheses of genital evolution (the lock-and-key, pleiotropy, and sexual selection hypotheses), and quantifying the form of selection targeting male genitals has played an important role in this endeavor. However, we currently know far less about selection targeting female genitals or how male and female genitals interact during mating. Here, we use formal selection analysis to show that genital size and shape is subject to strong multivariate stabilizing sexual selection in both sexes of the red flour beetle, Tribolium castaneum. Moreover, we show significant sexual selection on the covariance between the sexes for specific aspects of genital shape suggesting that male and female genitalia also interact to determine the successful transfer of a spermatophore during mating. Our work therefore highlights the important role that both male and female genital morphologies play in determining mating success and that these effects can occur independently, as well as through their interaction. Moreover, it cautions against the overly simplistic view that the sexual selection targeting genital morphology will always be directional in form and restricted primarily to males.
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Moran PA, Hunt J, Mitchell C, Ritchie MG, Bailey NW (2020). Sexual selection and population divergence III: Interspecific and intraspecific variation in mating signals.
Journal of Evolutionary Biology,
33(7), 990-1005.
Abstract:
Sexual selection and population divergence III: Interspecific and intraspecific variation in mating signals
A major challenge for studying the role of sexual selection in divergence and speciation is understanding the relative influence of different sexually selected signals on those processes in both intra- and interspecific contexts. Different signals may be more or less susceptible to co-option for species identification depending on the balance of sexual and ecological selection acting upon them. To examine this, we tested three predictions to explain geographic variation in long- versus short-range sexual signals across a 3,500 + km transect of two related Australian field cricket species (Teleogryllus spp.): (a) selection for species recognition, (b) environmental adaptation and (c) stochastic divergence. We measured male calling song and male and female cuticular hydrocarbons (CHCs) in offspring derived from wild populations, reared under common garden conditions. Song clearly differentiated the species, and no hybrids were observed suggesting that hybridization is rare or absent. Spatial variation in song was not predicted by geography, genetics or climatic factors in either species. In contrast, CHC divergence was strongly associated with an environmental gradient supporting the idea that the climatic environment selects more directly upon these chemical signals. In light of recently advocated models of diversification via ecological selection on secondary sexual traits, the different environmental associations we found for song and CHCs suggest that the impact of ecological selection on population divergence, and how that influences speciation, might be different for acoustic versus chemical signals.
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2019
Moran PA, Hunt J, Mitchell C, Ritchie MG, Bailey NW (2019). Behavioural mechanisms of sexual isolation involving multiple modalities and their inheritance.
J Evol Biol,
32(3), 243-258.
Abstract:
Behavioural mechanisms of sexual isolation involving multiple modalities and their inheritance.
Speciation research dissects the genetics and evolution of reproductive barriers between parental species. Hybrids are the "gatekeepers" of gene flow, so it is also important to understand the behavioural mechanisms and genetics of any potential isolation from their parental species. We tested the role of multiple behavioural barriers in reproductive isolation among closely related field crickets and their hybrids (Teleogryllus oceanicus and Teleogryllus commodus). These species hybridize in the laboratory, but the behaviour of hybrids is unusual and there is little evidence for gene flow in the wild. We found that heterospecific pairs exhibited reduced rates of courtship behaviour due to discrimination by both sexes, and that this behavioural isolation was symmetrical. However, hybrids were not sexually selected against and exhibited high rates of courtship behaviour even though hybrid females are sterile. Using reciprocal hybrid crosses, we characterized patterns of interspecific divergence and inheritance in key sexual traits that might underlie the mating patterns we found: calling song, courtship song and cuticular hydrocarbons (CHCs). Song traits exhibited both sex linkage and transgressive segregation, whereas CHCs exhibited only the latter. Calculations of the strength of isolation exerted by these sexual traits suggest that close-range signals are as important as long-distance signals in contributing to interspecific sexual isolation. The surprisingly weak mating barriers observed between hybrids and parental species highlight the need to examine reproductive isolating mechanisms and their genetic bases across different potential stages of introgressive hybridization.
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Sakaluk SK, Oldzej J, Poppe CJ, Harper JL, Rines IG, Hampton KJ, Duffield KR, Hunt J, Sadd BM (2019). Effects of inbreeding on life-history traits and sexual competency in decorated crickets.
Animal Behaviour,
155, 241-248.
Abstract:
Effects of inbreeding on life-history traits and sexual competency in decorated crickets
Although inbreeding depression in life-history traits has been well characterized, inbreeding effects on mating behaviour and sexually selected traits have been less well studied. Here, we assess levels of inbreeding depression in a number of fitness-related reproductive parameters of female decorated crickets, Gryllodes sigillatus. We predicted that due to direct negative effects of inbreeding and a potential trade-off between reproduction and current survival, as suggested by effects of inbreeding on immunity, inbred females would show significantly reduced reproductive output compared with outbred females. We also examined sex-specific effects of inbreeding on mating competency, focusing specifically on the female's decision to mount a male and the male's ability to transfer a spermatophore. We predicted that any inbreeding depression in sexual competency should be more evident in the success of spermatophore transfer than in female mounting propensity because of the tighter link between mating success and fitness in males than in females. Inbred females produced fewer offspring with longer development times compared with outbred females, results consistent with theory, as inbreeding depression is expected to be more severe for traits more tightly coupled with fitness. Inbreeding also had sex-specific effects on sexual competency. Inbred females were less likely to mount outbred males than were outbred females to mount inbred males. Inbred males were significantly less likely than outbred males to transfer a spermatophore regardless of female inbreeding status. These results reveal that inbreeding may have unexpected consequences for sexual competency and highlight the importance of considering mating behaviour when assessing effects of inbreeding within populations.
Abstract.
Duffield KR, Hampton KJ, Houslay TM, Hunt J, Sadd BM, Sakaluk SK (2019). Inbreeding alters context-dependent reproductive effort and immunity in male crickets.
J Evol Biol,
32(7), 731-741.
Abstract:
Inbreeding alters context-dependent reproductive effort and immunity in male crickets.
Infection can cause hosts to drastically alter their investment in key life-history traits of reproduction and defence. Infected individuals are expected to increase investment in defence (e.g. by increasing immune function) and, due to trade-offs, investment in other traits (e.g. current reproduction) should decrease. However, the terminal investment hypothesis postulates that decreased lifespan due to infection and the associated reduction in the expectation for future offspring will favour increased investment towards current reproduction. Variation in intrinsic condition will likely influence shifts in reproductive investment post-infection, but this is often not considered in such assessments. For example, the extent of inbreeding can significantly impact an individual's lifetime fitness and may influence its reproductive behaviour following a threat of infection. Here, we investigated the effects of inbreeding status on an individual's reproductive investment upon infection, including the propensity to terminally invest. Male crickets (Gryllodes sigillatus) from four genetically distinct inbred lines and one outbred line were subjected to a treatment from an increasing spectrum of simulated infection cue intensities, using heat-killed bacteria. We then measured reproductive effort (calling effort), survival and immune function (antibacterial activity, circulating haemocytes and haemocyte microaggregations). Inbred and outbred males diverged in how they responded to a low-dose infection cue: relative to unmanipulated males, outbred males decreased calling effort, whereas inbred males increased calling effort. Moreover, we found that inbred males exhibited higher antibacterial activity and numbers of circulating haemocytes compared with outbred males. These results suggest that an individual's inbreeding status may have consequences for context-dependent shifts in reproductive strategies, such as those triggered by infection.
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Nagarajan-Radha V, Rapkin J, Hunt J, Dowling DK (2019). Interactions Between Mitochondrial Haplotype and Dietary Macronutrient Ratios Confer Sex-Specific Effects on Longevity in Drosophila melanogaster.
J Gerontol a Biol Sci Med Sci,
74(10), 1573-1581.
Abstract:
Interactions Between Mitochondrial Haplotype and Dietary Macronutrient Ratios Confer Sex-Specific Effects on Longevity in Drosophila melanogaster.
Recent studies have demonstrated that modifications to the ratio of dietary macronutrients affect longevity in a diverse range of species. However, the degree to which levels of natural genotypic variation shape these dietary effects on longevity remains unclear. The mitochondria have long been linked to the aging process. The mitochondria possess their own genome, and previous studies have shown that mitochondrial genetic variation affects longevity in insects. Furthermore, the mitochondria are the sites in which dietary nutrients are oxidized to produce adenosine triphosphate, suggesting a capacity for dietary quality to mediate the link between mitochondrial genotype and longevity. Here, we measured longevity of male and female fruit flies, across a panel of genetic strains of Drosophila melanogaster, which vary only in their mitochondrial haplotype, when fed one of the two isocaloric diets that differed in their protein-to-carbohydrate ratio. The mitochondrial haplotype affected the longevity of flies, but the pattern of these effects differed across the two diets in males, but not in females. We discuss the implications of these results in relation to an evolutionary theory linking maternal inheritance of mitochondria to the accumulation of male-harming mitochondrial mutations, and to the theory exploring the evolution of phenotypic plasticity to novel environments.
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House CM, Rapkin J, Hunt J, Hosken DJ (2019). Operational sex ratio and density predict the potential for sexual selection in the broad-horned beetle.
Animal Behaviour,
152, 63-69.
Abstract:
Operational sex ratio and density predict the potential for sexual selection in the broad-horned beetle
Sexual selection can act on all aspects of the phenotype and the opportunity for selection (Is) sets its maximal strength. Popular approaches to alter is include the manipulation of the operational sex ratio (OSR) and/or density, with an increase in is predicted with a male-biased OSR and at higher density. However, debate continues regarding the utility of is to measure meaningful changes in the strength of selection, as changes in is with OSR and density may only reflect stochastic processes. Here we tested whether the manipulation of OSR and density alters is in the broad-horned flour beetle, Gnatocerus cornutus, a species where males are under intense sexual selection and the targets of selection are known. We also recorded the average number of fights and mating behaviour of individuals in our competitive arenas. We found significant main effects of OSR and density on is, with the opportunity for selection being highest in male-biased high-density treatments. There were also significant effects of OSR and density on the average number of matings, whereas only density influenced the average number of fights. These results suggest that manipulation of OSR and density influence the opportunity for sexual selection in G. cornutus and our observations of fighting and mating behaviour provide a proximate mechanism for the change in is.
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Full text.
Sakaluk SK, Duffield KR, Rapkin J, Sadd BM, Hunt J (2019). The troublesome gift: the spermatophylax as a purveyor of sexual conflict and coercion in crickets. In (Ed)
Advances in the Study of Behavior, 1-30.
Abstract:
The troublesome gift: the spermatophylax as a purveyor of sexual conflict and coercion in crickets
Abstract.
2018
Duffield KR, Hampton KJ, Houslay TM, Hunt J, Rapkin J, Sakaluk SK, Sadd BM (2018). Age-dependent variation in the terminal investment threshold in male crickets.
Evolution,
72(3), 578-589.
Abstract:
Age-dependent variation in the terminal investment threshold in male crickets.
The terminal investment hypothesis proposes that decreased expectation of future reproduction (e.g. arising from a threat to survival) should precipitate increased investment in current reproduction. The level at which a cue of decreased survival is sufficient to trigger terminal investment (i.e. the terminal investment threshold) may vary according to other factors that influence expectation for future reproduction. We test whether the terminal investment threshold varies with age in male crickets, using heat-killed bacteria to simulate an immune-inducing infection. We measured calling effort (a behavior essential for mating) and hemolymph antimicrobial activity in young and old males across a gradient of increasing infection cue intensity. There was a significant interaction between the infection cue and age in their effect on calling effort, confirming the existence of a dynamic terminal investment threshold: young males reduced effort at all infection levels, whereas old males increased effort at the highest levels relative to naïve individuals. A lack of a corresponding decrease in antibacterial activity suggests that altered reproductive effort is not traded against investment in this component of immunity. Collectively, these results support the existence of a dynamic terminal investment threshold, perhaps accounting for some of the conflicting evidence in support of terminal investment.
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Ruth Archer C, Basellini U, Hunt J, Simpson SJ, Lee KP, Baudisch A (2018). Diet has independent effects on the pace and shape of aging in Drosophila melanogaster.
Biogerontology,
19(1), 1-12.
Abstract:
Diet has independent effects on the pace and shape of aging in Drosophila melanogaster.
Studies examining how diet affects mortality risk over age typically characterise mortality using parameters such as aging rates, which condense how much and how quickly the risk of dying changes over time into a single measure. Demographers have suggested that decoupling the tempo and the magnitude of changing mortality risk may facilitate comparative analyses of mortality trajectories, but it is unclear what biologically meaningful information this approach offers. Here, we determine how the amount and ratio of protein and carbohydrate ingested by female Drosophila melanogaster affects how much mortality risk increases over a time-standardised life-course (the shape of aging) and the tempo at which animals live and die (the pace of aging). We find that pace values increased as flies consumed more carbohydrate but declined with increasing protein consumption. Shape values were independent of protein intake but were lowest in flies consuming ~90 μg of carbohydrate daily. As protein intake only affected the pace of aging, varying protein intake rescaled mortality trajectories (i.e. stretched or compressed survival curves), while varying carbohydrate consumption caused deviation from temporal rescaling (i.e. changed the topography of time-standardised survival curves), by affecting pace and shape. Clearly, the pace and shape of aging may vary independently in response to dietary manipulation. This suggests that there is the potential for pace and shape to evolve independently of one another and respond to different physiological processes. Understanding the mechanisms responsible for independent variation in pace and shape, may offer insight into the factors underlying diverse mortality trajectories.
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Rapkin J, Jensen K, House CM, Wilson AJ, Hunt J (2018). Genotype-by-sex-by-diet interactions for nutritional preference, dietary consumption, and lipid deposition in a field cricket.
Heredity (Edinb),
121(4), 361-373.
Abstract:
Genotype-by-sex-by-diet interactions for nutritional preference, dietary consumption, and lipid deposition in a field cricket.
Changes in feeding behaviour, especially the overconsumption of calories, has led to a rise in the rates of obesity, diabetes, and other associated disorders in humans and a range of animals inhabiting human-influenced environments. However, understanding the relative contribution of genes, the nutritional environment, and their interaction to dietary intake and lipid deposition in the sexes still remains a major challenge. By combining nutritional geometry with quantitative genetics, we determined the effect of genes, the nutritional environment, and their interaction on the total nutritional preference (TP), total diet eaten (TE), and lipid mass (LM) of male and female black field crickets (Teleogryllus commodus) fed one of four diet pairs (DPs) differing in the ratio of protein to carbohydrate and total nutritional content. We found abundant additive genetic variance for TP, TE, and LM in both sexes and across all four DPs, with significant genetic correlations between TE and TP and between TP and LM in males. We also found significant genotype-by-DP and genotype-by-sex-by-DP interactions for each trait and significant genotype-by-sex interactions for TE and LM. Complex interactions between genes, sex, and the nutritional environment, therefore, play an important role in nutrient regulation and lipid deposition in T. commodus. This finding may also help explain the increasing rate of obesity and the maintenance of sex differences in obesity observed across many animal species, including humans.
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Rapkin J, Jensen K, Archer CR, House CM, Sakaluk SK, Del Castillo E, Hunt J (2018). The geometry of nutrient space–based life-history trade-offs: Sex-specific effects of macronutrient intake on the trade-off between encapsulation ability and reproductive effort in decorated crickets.
American Naturalist,
191(4), 452-474.
Abstract:
The geometry of nutrient space–based life-history trade-offs: Sex-specific effects of macronutrient intake on the trade-off between encapsulation ability and reproductive effort in decorated crickets
Life-history theory assumes that traits compete for limited resources, resulting in trade-offs. The most commonly manipulated resource in empirical studies is the quantity or quality of diet. Recent studies using the geometric framework for nutrition, however, suggest that trade-offs are often regulated by the intake of specific nutrients, but a formal approach to identify and quantify the strength of such trade-offs is lacking. We posit that trade-offs occur whenever life-history traits are maximized in different regions of nutrient space, as evidenced by nonoverlapping 95% confidence regions of the global maximum for each trait and large angles (θ) between linear nutritional vectors and Euclidean distances (d) between global maxima. We then examined the effects of protein and carbohydrate intake on the trade-off between reproduction and aspects of immune function in male and female Gryllodes sigillatus. Female encapsulation ability and egg production increased with the intake of both nutrients, whereas male encapsulation ability increased with protein intake but calling effort increased with carbohydrate intake. The trade-offs between traits was therefore larger in males than in females, as demonstrated by significant negative correlations between the traits in males, nonoverlapping 95% confidence regions, and larger estimates of θ and d. Under dietary choice, the sexes had similar regulated intakes, but neither optimally regulated nutrient intake for maximal trait expression. We highlight the fact that greater consideration of specific nutrient intake is needed when examining nutrient space–based trade-offs.
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Kordsmeyer TL, Hunt J, Puts DA, Ostner J, Penke L (2018). The relative importance of intra- and intersexual selection on human male sexually dimorphic traits. Evolution and Human Behavior, 39(4), 424-436.
2017
Chenoweth SF, Hunt J (2017). Allowing nature to be nurture: a comment on Bailey et al. Behavioral Ecology, 29(1), 16-17.
Jensen K, Shearman M, Rapkin J, Carey MR, House CM, Hunt J (2017). Change in sex pheromone expression by nutritional shift in male cockroaches.
BEHAVIORAL ECOLOGY,
28(6), 1393-1401.
Author URL.
Maraqa MS, Griffin R, Sharma MD, Wilson AJ, Hunt J, Hosken DJ, House CM (2017). Constrained evolution of the sex comb in Drosophila simulans.
J Evol Biol,
30(2), 388-400.
Abstract:
Constrained evolution of the sex comb in Drosophila simulans.
Male fitness is dependent on sexual traits that influence mate acquisition (precopulatory sexual selection) and paternity (post-copulatory sexual selection), and although many studies have documented the form of selection in one or the other of these arenas, fewer have done it for both. Nonetheless, it appears that the dominant form of sexual selection is directional, although theoretically, populations should converge on peaks in the fitness surface, where selection is stabilizing. Many factors, however, can prevent populations from reaching adaptive peaks. Genetic constraints can be important if they prevent the development of highest fitness phenotypes, as can the direction of selection if it reverses across episodes of selection. In this study, we examine the evidence that these processes influence the evolution of the multivariate sex comb morphology of male Drosophila simulans. To do this, we conduct a quantitative genetic study together with a multivariate selection analysis to infer how the genetic architecture and selection interact. We find abundant genetic variance and covariance in elements of the sex comb. However, there was little evidence for directional selection in either arena. Significant nonlinear selection was detected prior to copulation when males were mated to nonvirgin females, and post-copulation during sperm offence (again with males mated to nonvirgins). Thus, contrary to our predictions, the evolution of the D. simulans sex comb is limited neither by genetic constraints nor by antagonistic selection between pre- and post-copulatory arenas, but nonlinear selection on the multivariate phenotype may prevent sex combs from evolving to reach some fitness maximizing optima.
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Malod K, Archer CR, Hunt J, Nicolson SW, Weldon CW (2017). Effects of macronutrient intake on the lifespan and fecundity of the marula fruit fly, Ceratitis cosyra (Tephritidae): Extreme lifespan in a host specialist.
Ecology and Evolution,
7(22), 9808-9817.
Abstract:
Effects of macronutrient intake on the lifespan and fecundity of the marula fruit fly, Ceratitis cosyra (Tephritidae): Extreme lifespan in a host specialist
In insects, lifespan and reproduction are strongly associated with nutrition. The ratio and amount of nutrients individuals consume affect their life expectancy and reproductive investment. The geometric framework (GF) enables us to explore how animals regulate their intake of multiple nutrients simultaneously and determine how these nutrients interact to affect life-history traits of interest. Studies using the GF on host-generalist tephritid flies have highlighted trade-offs between longevity and reproductive effort in females, mediated by the protein-to-carbohydrate (P:C) ratio that individuals consume. Here, we tested how P and C intake affect lifespan (LS) in both sexes, and female lifetime (LEP), and daily (DEP) egg production, in Ceratitis cosyra, a host-specialist tephritid fly. We then determined the P:C ratio that C. cosyra defends when offered a choice of foods. Female LS was optimized at a 0:1 P:C ratio, whereas to maximize their fecundity, females needed to consume a higher P:C ratio (LEP = 1:6 P:C; DEP = 1:2.5 P:C). In males, LS was also optimized at a low P:C ratio of 1:10. However, when given the opportunity to regulate their intake, both sexes actively defended a 1:3 P:C ratio, which is closer to the target for DEP than either LS or LEP. Our results show that female C. cosyra experienced a moderate trade-off between LS and fecundity. Moreover, the diets that maximized expression of LEP and DEP were of lower P:C ratio than those required for optimal expression of these traits in host-generalist tephritids or other generalist insects.
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Pincheira-Donoso D, Hunt J (2017). Fecundity selection theory: concepts and evidence.
Biol Rev Camb Philos Soc,
92(1), 341-356.
Abstract:
Fecundity selection theory: concepts and evidence.
Fitness results from an optimal balance between survival, mating success and fecundity. The interactions between these three components of fitness vary depending on the selective context, from positive covariation between them, to antagonistic pleiotropic relationships when fitness increases in one reduce the fitness of others. Therefore, elucidating the routes through which selection shapes life history and phenotypic adaptations via these fitness components is of primary significance to understanding ecological and evolutionary dynamics. However, while the fitness components mediated by natural (survival) and sexual (mating success) selection have been debated extensively from most possible perspectives, fecundity selection remains considerably less studied. Here, we review the theoretical basis, evidence and implications of fecundity selection as a driver of sex-specific adaptive evolution. Based on accumulating literature on the life-history, phenotypic and ecological aspects of fecundity, we (i) suggest a re-arrangement of the concepts of fecundity, whereby we coin the term 'transient fecundity' to refer to brood size per reproductive episode, while 'annual' and 'lifetime fecundity' should not be used interchangeably with 'transient fecundity' as they represent different life-history parameters; (ii) provide a generalized re-definition of the concept of fecundity selection as a mechanism that encompasses any traits that influence fecundity in any direction (from high to low) and in either sex; (iii) review the (macro)ecological basis of fecundity selection (e.g. ecological pressures that influence predictable spatial variation in fecundity); (iv) suggest that most ecological theories of fecundity selection should be tested in organisms other than birds; (v) argue that the longstanding fecundity selection hypothesis of female-biased sexual size dimorphism (SSD) has gained inconsistent support, that strong fecundity selection does not necessarily drive female-biased SSD, and that this form of SSD can be driven by other selective pressures; and (vi) discuss cases in which fecundity selection operates on males. This conceptual analysis of the theory of fecundity selection promises to help illuminate one of the central components of fitness and its contribution to adaptive evolution.
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Ower GD, Hunt J, Sakaluk SK (2017). Multivariate sexual selection on male tegmina in wild populations of sagebrush crickets, Cyphoderris strepitans (Orthoptera: Haglidae).
J Evol Biol,
30(2), 338-351.
Abstract:
Multivariate sexual selection on male tegmina in wild populations of sagebrush crickets, Cyphoderris strepitans (Orthoptera: Haglidae).
Although the strength and form of sexual selection on song in male crickets have been studied extensively, few studies have examined selection on the morphological structures that underlie variation in males' song, particularly in wild populations. Geometric morphometric techniques were used to measure sexual selection on the shape, size and symmetry of both top and bottom tegmina in wild populations of sagebrush crickets, a species in which nuptial feeding by females imposes an unambiguous phenotypic marker on males. The size of the tegmina negatively covaried with song dominant frequency and positively covaried with song pulse duration. Sexual selection was more intense on the bottom tegmen, conceivably because it interacts more freely with the subtegminal airspace, which may play a role in song amplification. An expanded coastal/subcostal region was one of the phenotypes strongly favoured by disruptive selection on the bottom tegmen, an adaptation that may form a more effective seal with the thorax to prevent noise cancellation. Directional selection also favoured increased symmetry in tegminal shape. Assuming more symmetrical males are better able to buffer against developmental noise, the song produced by these males may make them more attractive to females. Despite the strong stabilizing selection documented previously on the dominant frequency of the song, stabilizing selection on the resonator that regulates dominant frequency was surprisingly absent. Nonetheless, wing morphology had an important influence on song structure and appears to be subject to significant linear and nonlinear sexual selection through female mate choice.
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Rapkin J, Jensen K, House CM, Sakaluk SK, Sakaluk JK, Hunt J (2017). The complex interplay between macronutrient intake, cuticular hydrocarbon expression and mating success in male decorated crickets.
J Evol Biol,
30(4), 711-727.
Abstract:
The complex interplay between macronutrient intake, cuticular hydrocarbon expression and mating success in male decorated crickets.
The condition dependence of male sexual traits plays a central role in sexual selection theory. Relatively little, however, is known about the condition dependence of chemical signals used in mate choice and their subsequent effects on male mating success. Furthermore, few studies have isolated the specific nutrients responsible for condition-dependent variation in male sexual traits. Here, we used nutritional geometry to determine the effect of protein (P) and carbohydrate (C) intake on male cuticular hydrocarbon (CHC) expression and mating success in male decorated crickets (Gryllodes sigillatus). We show that both traits are maximized at a moderate-to-high intake of nutrients in a P:C ratio of 1 : 1.5. We also show that female precopulatory mate choice exerts a complex pattern of linear and quadratic sexual selection on this condition-dependent variation in male CHC expression. Structural equation modelling revealed that although the effect of nutrient intake on mating success is mediated through condition-dependent CHC expression, it is not exclusively so, suggesting that other traits must also play an important role. Collectively, our results suggest that the complex interplay between nutrient intake, CHC expression and mating success plays an important role in the operation of sexual selection in G. sigillatus.
Abstract.
Author URL.
2016
Tunstall P, Rapkin J, Gage M, Hunt J, House CM (2016). A ROLE FOR STABILIZING SEXUAL SELECTION FOR THE EVOLUTION OF MALE AND FEMALE GENITALIA IN a FLOUR BEETLE (Tribolium castaneum).
Author URL.
Bunning H, Bassett L, Clowser C, Rapkin J, Jensen K, House CM, Archer CR, Hunt J (2016). Dietary choice for a balanced nutrient intake increases the mean and reduces the variance in the reproductive performance of male and female cockroaches.
Ecology and Evolution,
6(14), 4711-4730.
Abstract:
Dietary choice for a balanced nutrient intake increases the mean and reduces the variance in the reproductive performance of male and female cockroaches
Sexual selection may cause dietary requirements for reproduction to diverge across the sexes and promote the evolution of different foraging strategies in males and females. However, our understanding of how the sexes regulate their nutrition and the effects that this has on sex-specific fitness is limited. We quantified how protein (P) and carbohydrate (C) intakes affect reproductive traits in male (pheromone expression) and female (clutch size and gestation time) cockroaches (Nauphoeta cinerea). We then determined how the sexes regulate their intake of nutrients when restricted to a single diet and when given dietary choice and how this affected expression of these important reproductive traits. Pheromone levels that improve male attractiveness, female clutch size and gestation time all peaked at a high daily intake of P:C in a 1:8 ratio. This is surprising because female insects typically require more P than males to maximize reproduction. The relatively low P requirement of females may reflect the action of cockroach endosymbionts that help recycle stored nitrogen for protein synthesis. When constrained to a single diet, both sexes prioritized regulating their daily intake of P over C, although this prioritization was stronger in females than males. When given the choice between diets, both sexes actively regulated their intake of nutrients at a 1:4.8 P:C ratio. The P:C ratio did not overlap exactly with the intake of nutrients that optimized reproductive trait expression. Despite this, cockroaches of both sexes that were given dietary choice generally improved the mean and reduced the variance in all reproductive traits we measured relative to animals fed a single diet from the diet choice pair. This pattern was not as strong when compared to the single best diet in our geometric array, suggesting that the relationship between nutrient balancing and reproduction is complex in this species.
Abstract.
House CM, Jensen K, Rapkin J, Lane S, Okada K, Hosken DJ, Hunt J (2016). Macronutrient balance mediates the growth of sexually selected weapons but not genitalia in male broad-horned beetles.
Functional Ecology,
30(5), 769-779.
Abstract:
Macronutrient balance mediates the growth of sexually selected weapons but not genitalia in male broad-horned beetles
Condition is defined as the pool of resources available to an individual that can be allocated to fitness-enhancing traits. Consequently, condition could influence developmental trade-offs if any occur. Although many studies have manipulated diet to demonstrate condition-dependent trait expression, few studies have determined the contribution of specific nutrients to condition or trade-offs. We used nutritional geometry to quantify the effects of dietary protein and carbohydrate content on larval performance and the development of adult morphology including body size as well as a primary and secondary sexually selected trait in male broad-horned beetles, Gnatocerus cornutus. We found that offspring survival, development rate and morphological traits were highly affected by dietary carbohydrate content and to a lesser extent by protein content and that all traits were maximized at a protein-to-carbohydrate ratio around 1:2. The absolute size of a secondary sexual character, the mandibles, had a heightened response to the increased availability and ratio of both macronutrients. Male genitalia, in contrast, were relatively insensitive to the increased availability of macronutrients. Overall, while nutrition influenced trait expression, the nutritional requirements of development rate and morphological traits were largely the same and resource acquisition seems to implement only weak trade-offs in this species. This finding contrasts with some resource constraint predictions, as beetles seem able to simultaneously meet the nutritional requirements of most traits.
Abstract.
Full text.
Rapkin J, Jensen K, Lane SM, House CM, Sakaluk SK, Hunt J (2016). Macronutrient intake regulates sexual conflict in decorated crickets.
J Evol Biol,
29(2), 395-406.
Abstract:
Macronutrient intake regulates sexual conflict in decorated crickets.
Sexual conflict results in a diversity of sex-specific adaptations, including chemical additions to ejaculates. Male decorated crickets (Gryllodes sigillatus) produce a gelatinous nuptial gift (the spermatophylax) that varies in size and free amino acid composition, which influences a female's willingness to fully consume this gift. Complete consumption of this gift maximizes sperm transfer through increased retention of the sperm-containing ampulla, but hinders post-copulatory mate choice. Here, we examine the effects of protein (P) and carbohydrate (C) intake on the weight and amino acid composition of the spermatophylax that describes its gustatory appeal to the female, as well as the ability of this gift to regulate sexual conflict via ampulla attachment time. Nutrient intake had similar effects on the expression of these traits with each maximized at a high intake of nutrients with a P : C ratio of 1 : 1.3. Under dietary choice, males actively regulated their nutrient intake but this regulation did not coincide with the peak of the nutritional landscape for any trait. Our results therefore demonstrate that a balanced intake of nutrients is central to regulating sexual conflict in G. sigillatus, but males are constrained from reaching the optima needed to bias the outcome of this conflict in their favour.
Abstract.
Author URL.
Houslay TM, Houslay KF, Hunt J, Rapkin J, Bussière LF (2016). Mating opportunities and energetic constraints drive variation in age-dependent sexual signalling.
Functional EcologyAbstract:
Mating opportunities and energetic constraints drive variation in age-dependent sexual signalling
When males repeatedly produce energetically expensive sexual signals, trade-offs between current and future investment can cause plasticity in age-dependent signalling. Such variation is often interpreted as alternate adaptive strategies: live fast and die young vs. slow and steady.
An alternative (yet rarely tested) explanation is that condition-dependent constraints on allocation cause variation in signalling with age (‘late bloomers’ do not have early investment options). Testing this hypothesis is challenging because resource acquisition and allocation are difficult to measure, and energetic reserves both affect and are affected by reproductive effort.
We simultaneously manipulated acquisition (through dietary nutrition) and access to potential mates (as a proxy for manipulating sexual trait allocation) in male decorated crickets (Gryllodes sigillatus), while measuring age- and signalling effort-mediated changes in energy storage components.
Increased diet quality caused increased signalling effort and energy storage, while access to females increased both the likelihood of and time spent signalling. Males with lower resource budgets signalled less, but still suffered energetic storage loss and viability costs.
Our results suggest that energetic constraints, rather than strategic resource accumulation, reduced signalling levels in males with lower resource acquisition ability. Our findings imply a non-adaptive explanation for age-dependent variation in sexual signalling, and an important role for energetic constraints in maintaining the honesty of costly behavioural displays.
Abstract.
Full text.
Hunt J, Dworkin I (2016). Multivariate Quantitative Genetics. In (Ed)
Encyclopedia of Evolutionary Biology, 71-76.
Abstract:
Multivariate Quantitative Genetics
Abstract.
Pascoal S, Mendrok M, Mitchell C, Wilson AJ, Hunt J, Bailey NW (2016). Sexual selection and population divergence I: the influence of socially flexible cuticular hydrocarbon expression in male field crickets (Teleogryllus oceanicus).
Evolution,
70(1), 82-97.
Abstract:
Sexual selection and population divergence I: the influence of socially flexible cuticular hydrocarbon expression in male field crickets (Teleogryllus oceanicus).
Debates about how coevolution of sexual traits and preferences might promote evolutionary diversification have permeated speciation research for over a century. Recent work demonstrates that the expression of such traits can be sensitive to variation in the social environment. Here, we examined social flexibility in a sexually selected male trait-cuticular hydrocarbon (CHC) profiles-in the field cricket Teleogryllus oceanicus and tested whether population genetic divergence predicts the extent or direction of social flexibility in allopatric populations. We manipulated male crickets' social environments during rearing and then characterized CHC profiles. CHC signatures varied considerably across populations and also in response to the social environment, but our prediction that increased social flexibility would be selected in more recently founded populations exposed to fluctuating demographic environments was unsupported. Furthermore, models examining the influence of drift and selection failed to support a role of sexual selection in driving population divergence in CHC profiles. Variation in social environments might alter the dynamics of sexual selection, but our results align with theoretical predictions that the role social flexibility plays in modulating evolutionary divergence depends critically on whether responses to variation in the social environment are homogeneous across populations, or whether gene by social environment interactions occur.
Abstract.
Author URL.
Full text.
2015
Steiger S, Capodeanu-Nägler A, Gershman SN, Weddle CB, Rapkin J, Sakaluk SK, Hunt J (2015). Female choice for male cuticular hydrocarbon profile in decorated crickets is not based on similarity to their own profile.
Journal of Evolutionary Biology,
28(12), 2175-2186.
Abstract:
Female choice for male cuticular hydrocarbon profile in decorated crickets is not based on similarity to their own profile
Indirect genetic benefits derived from female mate choice comprise additive (good genes) and nonadditive genetic benefits (genetic compatibility). Although good genes can be revealed by condition-dependent display traits, the mechanism by which compatibility alleles are detected is unclear because evaluation of the genetic similarity of a prospective mate requires the female to assess the genotype of the male and compare it to her own. Cuticular hydrocarbons (CHCs), lipids coating the exoskeleton of most insects, influence female mate choice in a number of species and offer a way for females to assess genetic similarity of prospective mates. Here, we determine whether female mate choice in decorated crickets is based on male CHCs and whether it is influenced by females' own CHC profiles. We used multivariate selection analysis to estimate the strength and form of selection acting on male CHCs through female mate choice, and employed different measures of multivariate dissimilarity to determine whether a female's preference for male CHCs is based on similarity to her own CHC profile. Female mating preferences were significantly influenced by CHC profiles of males. Male CHC attractiveness was not, however, contingent on the CHC profile of the choosing female, as certain male CHC phenotypes were equally attractive to most females, evidenced by significant linear and stabilizing selection gradients. These results suggest that additive genetic benefits, rather than nonadditive genetic benefits, accrue to female mate choice, in support of earlier work showing that CHC expression of males, but not females, is condition dependent.
Abstract.
Newcombe D, Hunt J, Mitchell C, Moore AJ (2015). Maternal effects and maternal selection arising from variation in allocation of free amino acid to eggs.
Ecol Evol,
5(12), 2397-2410.
Abstract:
Maternal effects and maternal selection arising from variation in allocation of free amino acid to eggs.
Maternal provisioning can have profound effects on offspring phenotypes, or maternal effects, especially early in life. One ubiquitous form of provisioning is in the makeup of egg. However, only a few studies examine the role of specific egg constituents in maternal effects, especially as they relate to maternal selection (a standardized selection gradient reflecting the covariance between maternal traits and offspring fitness). Here, we report on the evolutionary consequences of differences in maternal acquisition and allocation of amino acids to eggs. We manipulated acquisition by varying maternal diet (milkweed or sunflower) in the large milkweed bug, Oncopeltus fasciatus. Variation in allocation was detected by examining two source populations with different evolutionary histories and life-history response to sunflower as food. We measured amino acids composition in eggs in this 2 × 2 design and found significant effects of source population and maternal diet on egg and nymph mass and of source population, maternal diet, and their interaction on amino acid composition of eggs. We measured significant linear and quadratic maternal selection on offspring mass associated with variation in amino acid allocation. Visualizing the performance surface along the major axes of nonlinear selection and plotting the mean amino acid profile of eggs from each treatment onto the surface revealed a saddle-shaped fitness surface. While maternal selection appears to have influenced how females allocate amino acids, this maternal effect did not evolve equally in the two populations. Furthermore, none of the population means coincided with peak performance. Thus, we found that the composition of free amino acids in eggs was due to variation in both acquisition and allocation, which had significant fitness effects and created selection. However, although there can be an evolutionary response to novel food resources, females may be constrained from reaching phenotypic optima with regard to allocation of free amino acids.
Abstract.
Author URL.
Bunning H, Rapkin J, Belcher L, Archer CR, Jensen K, Hunt J (2015). Protein and carbohydrate intake influence sperm number and fertility in male cockroaches, but not sperm viability.
Proceedings of the Royal Society B: Biological Sciences,
282(1802).
Abstract:
Protein and carbohydrate intake influence sperm number and fertility in male cockroaches, but not sperm viability
It is commonly assumed that because males produce many, tiny sperm, they are cheap to produce. Recent work, however, suggests that sperm production is not cost-free. If sperm are costly to produce, sperm number and/or viability should be influenced by diet, and this has been documented in numerous species. Yet few studies have examined the exact nutrients responsible for mediating these effects. Here,we quantify the effects of protein (P) and carbohydrate (C) intake on sperm number and viability in the cockroach Nauphoeta cinerea, as well as the consequences for male fertility. We found the intake of P and C influenced sperm number, being maximized at a high intake of diets with a P: C ratio of 1: 2, but not sperm viability. The nutritional landscapes for male fertility and sperm number were closely aligned, suggesting that sperm number is the major determinant of male fertility in N. cinerea. Under dietary choice, males regulate nutrient intake at a P: C ratio of 1: 4.95, which is midway between the ratios needed to maximize sperm production and pre-copulatory attractiveness in this species. This raises the possibility that males regulate nutrient intake to balance the trade-off between pre- and post-copulatory traits in this species.
Abstract.
Bunning H, Rapkin J, Belcher L, Archer CR, Jensen K, Hunt J (2015). Protein and carbohydrate intake influence sperm number and fertility in male cockroaches, but not sperm viability.
Proc Biol Sci,
282(1802).
Abstract:
Protein and carbohydrate intake influence sperm number and fertility in male cockroaches, but not sperm viability.
It is commonly assumed that because males produce many, tiny sperm, they are cheap to produce. Recent work, however, suggests that sperm production is not cost-free. If sperm are costly to produce, sperm number and/or viability should be influenced by diet, and this has been documented in numerous species. Yet few studies have examined the exact nutrients responsible for mediating these effects. Here, we quantify the effects of protein (P) and carbohydrate (C) intake on sperm number and viability in the cockroach Nauphoeta cinerea, as well as the consequences for male fertility. We found the intake of P and C influenced sperm number, being maximized at a high intake of diets with a P : C ratio of 1 : 2, but not sperm viability. The nutritional landscapes for male fertility and sperm number were closely aligned, suggesting that sperm number is the major determinant of male fertility in N. cinerea. Under dietary choice, males regulate nutrient intake at a P : C ratio of 1 : 4.95, which is midway between the ratios needed to maximize sperm production and pre-copulatory attractiveness in this species. This raises the possibility that males regulate nutrient intake to balance the trade-off between pre- and post-copulatory traits in this species.
Abstract.
Author URL.
Lane SM, Solino JH, Mitchell C, Blount JD, Okada K, Hunt J, House CM (2015). Rival male chemical cues evoke changes in male pre- and post-copulatory investment in a flour beetle.
Behav Ecol,
26(4), 1021-1029.
Abstract:
Rival male chemical cues evoke changes in male pre- and post-copulatory investment in a flour beetle.
Males can gather information on the risk and intensity of sperm competition from their social environment. Recent studies have implicated chemosensory cues, for instance cuticular hydrocarbons (CHCs) in insects, as a key source of this information. Here, using the broad-horned flour beetle (Gnatocerus cornutus), we investigated the importance of contact-derived rival male CHCs in informing male perception of sperm competition risk and intensity. We experimentally perfumed virgin females with male CHCs via direct intersexual contact and measured male pre- and post-copulatory investment in response to this manipulation. Using chemical analysis, we verified that this treatment engendered changes to perfumed female CHC profiles, but did not make perfumed females "smell" mated. Despite this, males responded to these chemical changes. Males increased courtship effort under low levels of perceived competition (from 1-3 rivals), but significantly decreased courtship effort as perceived competition rose (from 3-5 rivals). Furthermore, our measurement of ejaculate investment showed that males allocated significantly more sperm to perfumed females than to control females. Together, these results suggest that changes in female chemical profile elicited by contact with rival males do not provide males with information on female mating status, but rather inform males of the presence of rivals within the population and thus provide a means for males to indirectly assess the risk of sperm competition.
Abstract.
Author URL.
Full text.
Houslay TM, Hunt J, Tinsley MC, Bussière LF (2015). Sex differences in the effects of juvenile and adult diet on age-dependent reproductive effort.
Journal of Evolutionary Biology,
28(5), 1067-1079.
Abstract:
Sex differences in the effects of juvenile and adult diet on age-dependent reproductive effort
Sexual selection should cause sex differences in patterns of resource allocation. When current and future reproductive effort trade off, variation in resource acquisition might further cause sex differences in age-dependent investment, or in sensitivity to changes in resource availability over time. However, the nature and prevalence of sex differences in age-dependent investment remain unclear. We manipulated resource acquisition at juvenile and adult stages in decorated crickets, Gryllodes sigillatus, and assessed effects on sex-specific allocation to age-dependent reproductive effort (calling in males, fecundity in females) and longevity. We predicted that the resource and time demands of egg production would result in relatively consistent female strategies across treatments, whereas male investment should depend sharply on diet. Contrary to expectations, female age-dependent reproductive effort diverged substantially across treatments, with resource-limited females showing much lower and later investment in reproduction; the highest fecundity was associated with intermediate lifespans. In contrast, long-lived males always signalled more than short-lived males, and male age-dependent reproductive effort did not depend on diet. We found consistently positive covariance between male reproductive effort and lifespan, whereas diet altered this covariance in females, revealing sex differences in the benefits of allocation to longevity. Our results support sex-specific selection on allocation patterns, but also suggest a simpler alternative: males may use social feedback to make allocation decisions and preferentially store resources as energetic reserves in its absence. Increased calling effort with age therefore could be caused by gradual resource accumulation, heightened mortality risk over time, and a lack of feedback from available mates.
Abstract.
Houslay TM, Hunt J, Tinsley MC, Bussière LF (2015). Sex differences in the effects of juvenile and adult diet on age-dependent reproductive effort.
J Evol Biol,
28(5), 1067-1079.
Abstract:
Sex differences in the effects of juvenile and adult diet on age-dependent reproductive effort.
Sexual selection should cause sex differences in patterns of resource allocation. When current and future reproductive effort trade off, variation in resource acquisition might further cause sex differences in age-dependent investment, or in sensitivity to changes in resource availability over time. However, the nature and prevalence of sex differences in age-dependent investment remain unclear. We manipulated resource acquisition at juvenile and adult stages in decorated crickets, Gryllodes sigillatus, and assessed effects on sex-specific allocation to age-dependent reproductive effort (calling in males, fecundity in females) and longevity. We predicted that the resource and time demands of egg production would result in relatively consistent female strategies across treatments, whereas male investment should depend sharply on diet. Contrary to expectations, female age-dependent reproductive effort diverged substantially across treatments, with resource-limited females showing much lower and later investment in reproduction; the highest fecundity was associated with intermediate lifespans. In contrast, long-lived males always signalled more than short-lived males, and male age-dependent reproductive effort did not depend on diet. We found consistently positive covariance between male reproductive effort and lifespan, whereas diet altered this covariance in females, revealing sex differences in the benefits of allocation to longevity. Our results support sex-specific selection on allocation patterns, but also suggest a simpler alternative: males may use social feedback to make allocation decisions and preferentially store resources as energetic reserves in its absence. Increased calling effort with age therefore could be caused by gradual resource accumulation, heightened mortality risk over time, and a lack of feedback from available mates.
Abstract.
Author URL.
Archer CR, Duffy E, Hosken DJ, Mokkonen M, Okada K, Oku K, Sharma MD, Hunt J (2015). Sex-specific effects of natural and sexual selection on the evolution of life span and ageing in Drosophila simulans.
Functional Ecology,
29(4), 562-569.
Abstract:
Sex-specific effects of natural and sexual selection on the evolution of life span and ageing in Drosophila simulans
Variation in the strength of age-dependent natural selection shapes differences in ageing rates across species and populations. Likewise, sexual selection can promote divergent patterns of senescence across the sexes. However, the effects of these processes on the evolution of ageing have largely been considered independently, and interactions between them are poorly understood. We use experimental evolution to investigate how natural and sexual selection affect life span and ageing in Drosophila simulans. Replicate populations were evolved under lifetime monogamy (relaxed sexual selection) or lifetime polyandry (elevated sexual selection) and at one of two temperatures, 25 °C (relaxed natural selection) or 27 °C (enhanced natural selection), in a fully factorial design. We measured longevity in 150 individually housed flies taken from each of three replicate populations per selection regime. We found that natural and sexual selection affected the evolution of life span via sex-specific effects on different ageing parameters (ageing rate vs. baseline mortality): natural selection reduced the rate of ageing in both sexes but increased male baseline mortality, while sexual selection elevated baseline mortality in both sexes but particularly in males. This means that sexual and natural selection interacted to reduce male life span but acted on female life span by independently affecting particular ageing parameters. Sex-specific effects of sexual and natural selection may help explain the diverse patterns of ageing seen in nature but complicate predictions about how ageing and life span evolve across the sexes.
Abstract.
Jensen K, McClure C, Priest NK, Hunt J (2015). Sex-specific effects of protein and carbohydrate intake on reproduction but not lifespan in Drosophila melanogaster.
Aging Cell,
14(4), 605-615.
Abstract:
Sex-specific effects of protein and carbohydrate intake on reproduction but not lifespan in Drosophila melanogaster.
Modest dietary restriction extends lifespan (LS) in a diverse range of taxa and typically has a larger effect in females than males. Traditionally, this has been attributed to a stronger trade-off between LS and reproduction in females than in males that is mediated by the intake of calories. Recent studies, however, suggest that it is the intake of specific nutrients that extends LS and mediates this trade-off. Here, we used the geometric framework (GF) to examine the sex-specific effects of protein (P) and carbohydrate (C) intake on LS and reproduction in Drosophila melanogaster. We found that LS was maximized at a high intake of C and a low intake of P in both sexes, whereas nutrient intake had divergent effects on reproduction. Male offspring production rate and LS were maximized at the same intake of nutrients, whereas female egg production rate was maximized at a high intake of diets with a P:C ratio of 1:2. This resulted in larger differences in nutrient-dependent optima for LS and reproduction in females than in males, as well as an optimal intake of nutrients for lifetime reproduction that differed between the sexes. Under dietary choice, the sexes followed similar feeding trajectories regulated around a P:C ratio of 1:4. Consequently, neither sex reached their nutritional optimum for lifetime reproduction, suggesting intralocus sexual conflict over nutrient optimization. Our study shows clear sex differences in the nutritional requirements of reproduction in D. melanogaster and joins the growing list of studies challenging the role of caloric restriction in extending LS.
Abstract.
Author URL.
Duffield KR, Rapkin J, Hunt J, Sadd BM, Sakaluk SK (2015). Terminal investment in gustatory appeal of male decorated cricket nuptial food gifts.
Author URL.
Duffield KR, Hunt J, Rapkin J, Sadd BM, Sakaluk SK (2015). Terminal investment in the gustatory appeal of nuptial food gifts in crickets.
Journal of Evolutionary Biology,
28(10), 1872-1881.
Abstract:
Terminal investment in the gustatory appeal of nuptial food gifts in crickets
Investment in current versus future reproduction represents a prominent trade-off in life-history theory and is likely dependent on an individual's life expectancy. The terminal investment hypothesis posits that a reduction in residual reproductive value (i.e. potential for future offspring) will result in increased investment in current reproduction. We tested the hypothesis that male decorated crickets (Gryllodes sigillatus), when cued to their impending mortality, should increase their reproductive effort by altering the composition of their nuptial food gifts (i.e. spermatophylaxes) to increase their gustatory appeal to females. Using a repeated-measures design, we analysed the amino acid composition of spermatophylaxes derived from males both before and after injection of either a saline control or a solution of heat-killed bacteria. The latter, although nonpathogenic, represents an immune challenge that may signal an impending survival threat. One principal component explaining amino acid variation in spermatophylaxes, characterized by a high loading to histidine, was significantly lower in immune-challenged versus control males. The relevance of this difference for the gustatory appeal of gifts to females was assessed by mapping spermatophylax composition onto a fitness surface derived in an earlier study identifying the amino acid composition of spermatophylaxes preferred by females. We found that immune-challenged males maintained the level of attractiveness of their gifts post-treatment, whereas control males produced significantly less attractive gifts post-injection. These results are consistent with the hypothesis that cues of a survival-threatening infection stimulate terminal investment in male decorated crickets with respect to the gustatory appeal of their nuptial food gifts.
Abstract.
Archer CR, Hempenstall S, Royle NJ, Selman C, Willis S, Rapkin J, Blount JD, Hunt J (2015). Testing the Effects of DL-Alpha-Tocopherol Supplementation on Oxidative Damage, Total Antioxidant Protection and the Sex-Specific Responses of Reproductive Effort and Lifespan to Dietary Manipulation in Australian Field Crickets (Teleogryllus commodus).
Antioxidants (Basel),
4(4), 768-792.
Abstract:
Testing the Effects of DL-Alpha-Tocopherol Supplementation on Oxidative Damage, Total Antioxidant Protection and the Sex-Specific Responses of Reproductive Effort and Lifespan to Dietary Manipulation in Australian Field Crickets (Teleogryllus commodus).
The oxidative stress theory predicts that the accumulation of oxidative damage causes aging. More generally, oxidative damage could be a cost of reproduction that reduces survival. Both of these hypotheses have mixed empirical support. To better understand the life-history consequences of oxidative damage, we fed male and female Australian field crickets (Teleogryllus commodus) four diets differing in their protein and carbohydrate content, which have sex-specific effects on reproductive effort and lifespan. We supplemented half of these crickets with the vitamin E isoform DL-alpha-tocopherol and measured the effects of nutrient intake on lifespan, reproduction, oxidative damage and antioxidant protection. We found a clear trade-off between reproductive effort and lifespan in females but not in males. In direct contrast to the oxidative stress theory, crickets fed diets that improved their lifespan had high levels of oxidative damage to proteins. Supplementation with DL-alpha-tocopherol did not significantly improve lifespan or reproductive effort. However, males fed diets that increased their reproductive investment experienced high oxidative damage to proteins. While this suggests that male reproductive effort could elevate oxidative damage, this was not associated with reduced male survival. Overall, these results provide little evidence that oxidative damage plays a central role in mediating life-history trade-offs in T. commodus.
Abstract.
Author URL.
Archer CR, Hunt J (2015). Understanding the link between sexual selection, sexual conflict and aging using crickets as a model.
Experimental Gerontology,
71, 4-13.
Abstract:
Understanding the link between sexual selection, sexual conflict and aging using crickets as a model
Aging evolved because the strength of natural selection declines over the lifetime of most organisms. Weak natural selection late in life allows the accumulation of deleterious mutations and may favor alleles that have positive effects on fitness early in life, but costly pleiotropic effects expressed later on. While this decline in natural selection is central to longstanding evolutionary explanations for aging, a role for sexual selection and sexual conflict in the evolution of lifespan and aging has only been identified recently. Testing how sexual selection and sexual conflict affect lifespan and aging is challenging as it requires quantifying male age-dependent reproductive success. This is difficult in the invertebrate model organisms traditionally used in aging research. Research using crickets (Orthoptera: Gryllidae), where reproductive investment can be easily measured in both sexes, has offered exciting and novel insights into how sexual selection and sexual conflict affect the evolution of aging, both in the laboratory and in the wild. Here we discuss how sexual selection and sexual conflict can be integrated alongside evolutionary and mechanistic theories of aging using crickets as a model. We then highlight the potential for research using crickets to further advance our understanding of lifespan and aging.
Abstract.
Archer CR, Hunt J (2015). Understanding the link between sexual selection, sexual conflict and aging using crickets as a model.
Exp Gerontol,
71, 4-13.
Abstract:
Understanding the link between sexual selection, sexual conflict and aging using crickets as a model.
Aging evolved because the strength of natural selection declines over the lifetime of most organisms. Weak natural selection late in life allows the accumulation of deleterious mutations and may favor alleles that have positive effects on fitness early in life, but costly pleiotropic effects expressed later on. While this decline in natural selection is central to longstanding evolutionary explanations for aging, a role for sexual selection and sexual conflict in the evolution of lifespan and aging has only been identified recently. Testing how sexual selection and sexual conflict affect lifespan and aging is challenging as it requires quantifying male age-dependent reproductive success. This is difficult in the invertebrate model organisms traditionally used in aging research. Research using crickets (Orthoptera: Gryllidae), where reproductive investment can be easily measured in both sexes, has offered exciting and novel insights into how sexual selection and sexual conflict affect the evolution of aging, both in the laboratory and in the wild. Here we discuss how sexual selection and sexual conflict can be integrated alongside evolutionary and mechanistic theories of aging using crickets as a model. We then highlight the potential for research using crickets to further advance our understanding of lifespan and aging.
Abstract.
Author URL.
Gwynne DT, Punzalan D, Hunt J (2015). Viability selection on female fly finery in the wild.
Biological Journal of the Linnean Society,
116(3), 530-540.
Abstract:
Viability selection on female fly finery in the wild
Female ornaments have evolved in a few taxa in which females compete for access to important resources provided by their mates. However, the effects of these sexually selected traits on survival have not been studied. Elaborate leg-scale and/or abdominal ornaments are displayed by females of some Rhamphomyia dance flies (Diptera: Empididae) to flying males carrying prey gifts (females do not hunt). Previous analyses have shown significant sexual selection on these female traits. We studied viability selection on the traits by sampling the webs of two spider species and comparing prey R. longicauda females to survivors. We also investigated viability selection from one of the spiders over two seasons. We found that the direction of viability selection on R. longicauda from sticky Tetragnatha spider webs was consistent over two seasons. For abdominal ornaments the form of viability selection was positive and primarily directional (linear). Viability selection also favoured shorter tibiae but there was no significant selection on the size of residual tibial scale area. However, with the addition of dance fly kills from the non-sticky, leaf-covering webs of a Dictyna spider, abundant in only one of the seasons, the overall direction of viability selection favoured larger tibial ornaments. While noting that this viability selection on tibial scale ornaments may be a statistical artefact of the fewer traits in the two-predator analysis (abdominal structures were missing from most Dictyna prey), we suggest that simple differences in the natural history of selective agents causing mortality may partly explain the variation in whether sexual traits are under viability selection. Viability selection on ornamental traits may vary greatly between seasons with changes in the abundances of different natural enemies so that net directional selection on these traits over many generations may be weak.
Abstract.
Pauchet Y, Wielsch N, Wilkinson PA, Sakaluk SK, Svatoš A, ffrench-Constant RH, Hunt J, Heckel DG (2015). What's in the Gift? Towards a Molecular Dissection of Nuptial Feeding in a Cricket.
PLoS One,
10(10).
Abstract:
What's in the Gift? Towards a Molecular Dissection of Nuptial Feeding in a Cricket.
Nuptial gifts produced by males and transferred to females during copulation are common in insects. Yet, their precise composition and subsequent physiological effects on the female recipient remain unresolved. Male decorated crickets Gryllodes sigillatus transfer a spermatophore to the female during copulation that is composed of an edible gift, the spermatophylax, and the ampulla that contains the ejaculate. After transfer of the spermatophore, the female detaches the spermatophylax and starts to eat it while sperm from the ampulla are evacuated into the female reproductive tract. When the female has finished consuming the spermatophylax, she detaches the ampulla and terminates sperm transfer. Hence, one simple function of the spermatophylax is to ensure complete sperm transfer by distracting the female from prematurely removing the ampulla. However, the majority of orally active components of the spermatophylax itself and their subsequent effects on female behavior have not been identified. Here, we report the first analysis of the proteome of the G. sigillatus spermatophylax and the transcriptome of the male accessory glands that make these proteins. The accessory gland transcriptome was assembled into 17,691 transcripts whilst about 30 proteins were detected within the mature spermatophylax itself. of these 30 proteins, 18 were encoded by accessory gland encoded messages. Most spermatophylax proteins show no similarity to proteins with known biological functions and are therefore largely novel. A spermatophylax protein shows similarity to protease inhibitors suggesting that it may protect the biologically active components from digestion within the gut of the female recipient. Another protein shares similarity with previously characterized insect polypeptide growth factors suggesting that it may play a role in altering female reproductive physiology concurrent with fertilization. Characterization of the spermatophylax proteome provides the first step in identifying the genes encoding these proteins in males and in understanding their biological functions in the female recipient.
Abstract.
Author URL.
Full text.
2014
Hosken DJ, Hunt J (2014). Conclusions and Final Thoughts. In (Ed) Genotype-by-Environment Interactions and Sexual Selection, 331-334.
Ingleby FC, Hosken DJ, Flowers K, Hawkes MF, Lane SM, Rapkin J, House CM, Sharma MD, Hunt J (2014). Environmental heterogeneity, multivariate sexual selection and genetic constraints on cuticular hydrocarbons in Drosophila simulans.
Journal of Evolutionary Biology,
27(4), 700-713.
Abstract:
Environmental heterogeneity, multivariate sexual selection and genetic constraints on cuticular hydrocarbons in Drosophila simulans
Sexual selection is responsible for the evolution of many elaborate traits, but sexual trait evolution could be influenced by opposing natural selection as well as genetic constraints. As such, the evolution of sexual traits could depend heavily on the environment if trait expression and attractiveness vary between environments. Here, male Drosophila simulans were reared across a range of diets and temperatures, and we examined differences between these environments in terms of (i) the expression of male cuticular hydrocarbons (CHCs) and (ii) which male CHC profiles were most attractive to females. Temperature had a strong effect on male CHC expression, whereas the effect of diet was weaker. Male CHCs were subject to complex patterns of directional, quadratic and correlational sexual selection, and we found differences between environments in the combination of male CHCs that were most attractive to females, with clearer differences between diets than between temperatures. We also show that genetic covariance between environments is likely to cause a constraint on independent CHC evolution between environments. Our results demonstrate that even across the narrow range of environmental variation studied here, predicting the outcome of sexual selection can be extremely complicated, suggesting that studies ignoring multiple traits or environments may provide an over-simplified view of the evolution of sexual traits. © 2014 European Society for Evolutionary Biology.
Abstract.
Ingleby FC, Hosken DJ, Flowers K, Hawkes MF, Lane SM, Rapkin J, House CM, Sharma MD, Hunt J (2014). Environmental heterogeneity, multivariate sexual selection and genetic constraints on cuticular hydrocarbons in Drosophila simulans. Journal of Evolutionary Biology
Pitchers W, Wolf JB, Tregenza T, Hunt J, Dworkin I (2014). Evolutionary rates for multivariate traits: the role of selection and genetic variation.
Philos Trans R Soc Lond B Biol Sci,
369(1649).
Abstract:
Evolutionary rates for multivariate traits: the role of selection and genetic variation.
A fundamental question in evolutionary biology is the relative importance of selection and genetic architecture in determining evolutionary rates. Adaptive evolution can be described by the multivariate breeders' equation (Δz(-)=Gβ), which predicts evolutionary change for a suite of phenotypic traits (Δz(-)) as a product of directional selection acting on them (β) and the genetic variance-covariance matrix for those traits (G ). Despite being empirically challenging to estimate, there are enough published estimates of G and β to allow for synthesis of general patterns across species. We use published estimates to test the hypotheses that there are systematic differences in the rate of evolution among trait types, and that these differences are, in part, due to genetic architecture. We find some evidence that sexually selected traits exhibit faster rates of evolution compared with life-history or morphological traits. This difference does not appear to be related to stronger selection on sexually selected traits. Using numerous proposed approaches to quantifying the shape, size and structure of G, we examine how these parameters relate to one another, and how they vary among taxonomic and trait groupings. Despite considerable variation, they do not explain the observed differences in evolutionary rates.
Abstract.
Author URL.
Full text.
Hunt J, Hosken DJ (eds)(2014). Genotype-by-Environment Interactions and Sexual Selection. , Wiley Blackwell.
Wolf JB, Royle NJ, Hunt J (2014). Genotype-by-Environment Interactions when the Social Environment Contains Genes. In (Ed)
Genotype-by-Environment Interactions and Sexual Selection, 63-97.
Abstract:
Genotype-by-Environment Interactions when the Social Environment Contains Genes
Abstract.
Jensen K, Simpson SJ, Nielsen VH, Hunt J, Raubenheimer D, Mayntz D (2014). Nutrient-specific compensatory feeding in a mammalian carnivore, the mink, Neovison vison.
Br J Nutr,
112(7), 1226-1233.
Abstract:
Nutrient-specific compensatory feeding in a mammalian carnivore, the mink, Neovison vison.
Balancing of macronutrient intake has only recently been demonstrated in predators. In particular, the ability to regulate carbohydrate intake is little studied in obligate carnivores, as carbohydrate is present at very low concentrations in prey animal tissue. In the present study, we determined whether American mink (Neovison vison) would compensate for dietary nutritional imbalances by foraging for complementary macronutrients (protein, lipid and carbohydrate) when subsequently given a dietary choice. We used three food pairings, within which two macronutrients differed relative to each other (high v. low concentration), while the third was kept at a constant level. The mink were first restricted to a single nutritionally imbalanced food for 7 d and then given a free choice to feed from the same food or a nutritionally complementary food for three consecutive days. When restricted to nutritionally imbalanced foods, the mink were willing to overingest protein only to a certain level ('ceiling'). When subsequently given a choice, the mink compensated for the period of nutritional imbalance by selecting the nutritionally complementary food in the food choice pairing. Notably, this rebalancing occurred for all the three macronutrients, including carbohydrate, which is particularly interesting as carbohydrate is not a major macronutrient for obligate carnivores in nature. However, there was also a ceiling to carbohydrate intake, as has been demonstrated previously in domestic cats. The results of the present study show that mink regulate their intake of all the three macronutrients within limits imposed by ceilings on protein and carbohydrate intake and that they will compensate for a period of nutritional imbalance by subsequently selecting nutritionally complementary foods.
Abstract.
Author URL.
Hosken DJ, Hunt J (2014). Preface.
Capodeanu-Nägler A, Rapkin J, Sakaluk SK, Hunt J, Steiger S (2014). Self-recognition in crickets via on-line processing.
Curr Biol,
24(23), R1117-R1118.
Author URL.
Ingleby FC, Hosken DJ, Hunt J (2014). Sexual Selection and Genotype-by-Environment Interactions in Drosophila Cuticular Hydrocarbons. In (Ed)
Genotype-by-Environment Interactions and Sexual Selection, 265-281.
Abstract:
Sexual Selection and Genotype-by-Environment Interactions in Drosophila Cuticular Hydrocarbons
Abstract.
Sakaluk SK, Weddle C, Hunt J (2014). Signal Reliability, Sex-Specific Genotype-by-Environment Interactions in Cuticular Hydrocarbon Expression, and the Maintenance of Polyandry through Chemosensory Self-Referencing in Decorated Crickets, Gryllodes sigillatus. In (Ed)
Genotype-by-Environment Interactions and Sexual Selection, 312-330.
Abstract:
Signal Reliability, Sex-Specific Genotype-by-Environment Interactions in Cuticular Hydrocarbon Expression, and the Maintenance of Polyandry through Chemosensory Self-Referencing in Decorated Crickets, Gryllodes sigillatus
Abstract.
Pitchers WR, Klingenberg CP, Tregenza T, Hunt J, Dworkin I (2014). The potential influence of morphology on the evolutionary divergence of an acoustic signal.
J Evol Biol,
27(10), 2163-2176.
Abstract:
The potential influence of morphology on the evolutionary divergence of an acoustic signal.
The evolution of acoustic behaviour and that of the morphological traits mediating its production are often coupled. Lack of variation in the underlying morphology of signalling traits has the potential to constrain signal evolution. This relationship is particularly likely in field crickets, where males produce acoustic advertisement signals to attract females by stridulating with specialized structures on their forewings. In this study, we characterize the size and geometric shape of the forewings of males from six allopatric populations of the black field cricket (Teleogryllus commodus) known to have divergent advertisement calls. We sample from each of these populations using both wild-caught and common-garden-reared cohorts, allowing us to test for multivariate relationships between wing morphology and call structure. We show that the allometry of shape has diverged across populations. However, there was a surprisingly small amount of covariation between wing shape and call structure within populations. Given the importance of male size for sexual selection in crickets, the divergence we observe among populations has the potential to influence the evolution of advertisement calls in this species.
Abstract.
Author URL.
2013
Jensen K, Engelke S, Simpson SJ, Mayntz D, Hunt J (2013). Balancing of specific nutrients and subsequent growth and body composition in the slug Arion lusitanicus.
Physiol Behav,
122, 84-92.
Abstract:
Balancing of specific nutrients and subsequent growth and body composition in the slug Arion lusitanicus.
Feeding generalists typically occupy broad ecological niches and so are potentially pre-adapted to a range of novel food objects. In northern Europe, the slug Arion lusitanicus has spread rapidly as an invasive species and a serious horticultural and agricultural pest. We used nutritional geometry to analyze nutrient balancing capabilities and consequences for performance in A. lusitanicus when provided with one of three nutritionally fixed diets or when given dietary choice. The slugs over-ingested high amounts of the most abundant nutrient in order to get more of the limited nutrient. However, they regulated protein intake more tightly than carbohydrate intake resulting in a very high food intake when fed a protein-poor diet. Growth and body composition were highly affected by the nutrient balance of their diet. When given the choice to feed from two nutritionally different diets, the slugs selected an intake balance of protein and carbohydrate with sufficient precision to maximize growth. Nutrient utilization efficiency increased with increasing deficiency of the specific nutrient in the diet. Ingested carbohydrate was more efficiently stored as lipid in slugs fed more carbohydrate-poor diets, and ingested nitrogen was more efficiently incorporated into slug bodies in slugs fed more protein-poor diets. Our experiments suggest that the evolved behavioral and physiological regulatory capacities of A. lusitanicus may explain some of the success that this slug experiences as an invasive species. We furthermore propose that invasive species might be more dependent on high protein availability in the environment than non-invasive species.
Abstract.
Author URL.
Gershman SN, Hunt J, Sakaluk SK (2013). Food fight: Sexual conflict over free amino acids in the nuptial gifts of male decorated crickets. Journal of Evolutionary Biology
Gershman SN, Hunt J, Sakaluk SK (2013). Food fight: Sexual conflict over free amino acids in the nuptial gifts of male decorated crickets.
Journal of Evolutionary Biology,
26(4), 693-704.
Abstract:
Food fight: Sexual conflict over free amino acids in the nuptial gifts of male decorated crickets
In decorated crickets, Gryllodes sigillatus, the spermatophore that a male transfers at mating includes a gelatinous spermatophylax that the female consumes, delaying her removal of the sperm-filled ampulla. Male fertilization success increases with the length of time females spend feeding on the spermatophylax, while females may benefit by prematurely discarding the spermatophylaxes of undesirable males. This sexual conflict should favour males that produce increasingly appealing spermatophylaxes, and females that resist this manipulation. To determine the genetic basis of female spermatophylax feeding behaviour, we fed spermatophylaxes to females of nine inbred lines and found that female genotype had a major influence on spermatophylax feeding duration. The amino acid composition of the spermatophylax was also significantly heritable. There was a positive genetic correlation between spermatophylax feeding duration and the gustatory appeal of the spermatophylax. This correlation suggests that genes expressed in males that produce more manipulative spermatophylaxes are positively linked to genes expressed in females that make them more vulnerable to manipulation. Outbred females spent less time feeding on spermatophylaxes than inbred females, and thus showed greater resistance to male manipulation. Further, in a nonspermatophylax producing cricket (Acheta domesticus), females were significantly more prone to feeding on spermatophylaxes than outbred female Gryllodes. Collectively, these results suggest a history of sexually antagonistic coevolution over the consumption of nuptial food gifts. © 2013 the Authors. Journal of Evolutionary Biology © 2013 European Society for Evolutionary Biology.
Abstract.
Ingleby FC, Hunt J, Hosken DJ (2013). Genotype-by-Environment Interactions for Female Mate Choice of Male Cuticular Hydrocarbons in Drosophila simulans.
PLoS ONE,
8(6).
Abstract:
Genotype-by-Environment Interactions for Female Mate Choice of Male Cuticular Hydrocarbons in Drosophila simulans
Recent research has highlighted the potential importance of environmental and genotype-by-environment (G×E) variation in sexual selection, but most studies have focussed on the expression of male sexual traits. Consequently, our understanding of genetic variation for plasticity in female mate choice is extremely poor. In this study we examine the genetics of female mate choice in Drosophila simulans using isolines reared across two post-eclosion temperatures. There was evidence for G×Es in female choosiness and preference, which suggests that the evolution of female mate choice behaviour could differ across environments. However, the ranked order of preferred males was consistent across females and environments, so the same males are favoured by mate choice in spite of G×Es. Our study highlights the importance of taking cross-environment perspectives in order to gain a more comprehensive understanding of the operation of sexual selection. © 2013 Ingleby et al.
Abstract.
Full text.
Ingleby FC, Hunt J, Hosken DJ (2013). Heritability of male attractiveness persists despite evidence for unreliable sexual signals in Drosophila simulans.
J Evol Biol,
26(2), 311-324.
Abstract:
Heritability of male attractiveness persists despite evidence for unreliable sexual signals in Drosophila simulans.
Sexual signals can be used to attract mates, but to be honest indicators of signaller quality they need to convey information reliably. However, environmental variation and genotype-by-environment (G × E) interactions have the potential to compromise the reliability of sexual signals. Here, we test the reliability of cuticular hydrocarbons (CHCs) as signals of heritable aspects of male attractiveness in Drosophila simulans. We examined the heritability of male attractiveness and a measure of the difference between fathers' and sons' CHC profiles across dietary and temperature environments. Our results show that environmental heterogeneity disrupts the similarity of some components of father and son CHC profile. However, overall male attractiveness is heritable within and across environments, so that sire attractiveness is a good predictor of son attractiveness even with environmental heterogeneity. This suggests that although some male CHC signals are unreliable, attractive genotypes retain their attractiveness across environments on average.
Abstract.
Author URL.
Pitchers WR, Brooks R, Jennions MD, Tregenza T, Dworkin I, Hunt J (2013). Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus.
Journal of Evolutionary Biology,
26(5), 1060-1078.
Abstract:
Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus
Phenotypic integration and plasticity are central to our understanding of how complex phenotypic traits evolve. Evolutionary change in complex quantitative traits can be predicted using the multivariate breeders' equation, but such predictions are only accurate if the matrices involved are stable over evolutionary time. Recent study, however, suggests that these matrices are temporally plastic, spatially variable and themselves evolvable. The data available on phenotypic variance-covariance matrix (P) stability are sparse, and largely focused on morphological traits. Here, we compared P for the structure of the complex sexual advertisement call of six divergent allopatric populations of the Australian black field cricket, Teleogryllus commodus. We measured a subset of calls from wild-caught crickets from each of the populations and then a second subset after rearing crickets under common-garden conditions for three generations. In a second experiment, crickets from each population were reared in the laboratory on high- and low-nutrient diets and their calls recorded. In both experiments, we estimated P for call traits and used multiple methods to compare them statistically (Flury hierarchy, geometric subspace comparisons and random skewers). Despite considerable variation in means and variances of individual call traits, the structure of P was largely conserved among populations, across generations and between our rearing diets. Our finding that P remains largely stable, among populations and between environmental conditions, suggests that selection has preserved the structure of call traits in order that they can function as an integrated unit. © 2013 the Authors. © 2013 European Society for Evolutionary Biology.
Abstract.
Pitchers WR, Brooks R, Jennions MD, Tregenza T, Dworkin I, Hunt J (2013). Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus.
J Evol Biol,
26(5), 1060-1078.
Abstract:
Limited plasticity in the phenotypic variance-covariance matrix for male advertisement calls in the black field cricket, Teleogryllus commodus.
Phenotypic integration and plasticity are central to our understanding of how complex phenotypic traits evolve. Evolutionary change in complex quantitative traits can be predicted using the multivariate breeders' equation, but such predictions are only accurate if the matrices involved are stable over evolutionary time. Recent study, however, suggests that these matrices are temporally plastic, spatially variable and themselves evolvable. The data available on phenotypic variance-covariance matrix (P) stability are sparse, and largely focused on morphological traits. Here, we compared P for the structure of the complex sexual advertisement call of six divergent allopatric populations of the Australian black field cricket, Teleogryllus commodus. We measured a subset of calls from wild-caught crickets from each of the populations and then a second subset after rearing crickets under common-garden conditions for three generations. In a second experiment, crickets from each population were reared in the laboratory on high- and low-nutrient diets and their calls recorded. In both experiments, we estimated P for call traits and used multiple methods to compare them statistically (Flury hierarchy, geometric subspace comparisons and random skewers). Despite considerable variation in means and variances of individual call traits, the structure of P was largely conserved among populations, across generations and between our rearing diets. Our finding that P remains largely stable, among populations and between environmental conditions, suggests that selection has preserved the structure of call traits in order that they can function as an integrated unit.
Abstract.
Author URL.
Ower GD, Judge KA, Steiger S, Caron KJ, Smith RA, Hunt J, Sakaluk SK (2013). Multivariate sexual selection on male song structure in wild populations of sagebrush crickets, Cyphoderris strepitans (Orthoptera: Haglidae).
ECOLOGY AND EVOLUTION,
3(10), 3590-3603.
Author URL.
Archer CR, Sakaluk SK, Selman C, Royle NJ, Hunt J (2013). Oxidative stress and the evolution of sex differences in life span and ageing in the decorated cricket, Gryllodes sigillatus.
Evolution,
67(3), 620-634.
Abstract:
Oxidative stress and the evolution of sex differences in life span and ageing in the decorated cricket, Gryllodes sigillatus
The Free Radical Theory of Ageing (FRTA) predicts that oxidative stress, induced when levels of reactive oxygen species exceed the capacity of antioxidant defenses, causes ageing. Recently, it has also been argued that oxidative damage may mediate important life-history trade-offs. Here, we use inbred lines of the decorated cricket, Gryllodes sigillatus, to estimate the genetic (co)variance between age-dependent reproductive effort, life span, ageing, oxidative damage, and total antioxidant capacity within and between the sexes. The FRTA predicts that oxidative damage should accumulate with age and negatively correlate with life span. We find that protein oxidation is greater in the shorter lived sex (females) and negatively genetically correlated with life span in both sexes. However, oxidative damage did not accumulate with age in either sex. Previously we have shown antagonistic pleiotropy between the genes for early-life reproductive effort and ageing rate in both sexes, although this was stronger in females. In females, we find that elevated fecundity early in life is associated with greater protein oxidation later in life, which is in turn positively correlated with the rate of ageing. Our results provide mixed support for the FRTA but suggest that oxidative stress may mediate sex-specific life-history strategies in G. sigillatus. © 2012 the Author(s). Evolution © 2012 the Society for the Study of Evolution.
Abstract.
Hill AK, Hunt J, Welling LLM, Cárdenas RA, Rotella MA, Wheatley JR, Dawood K, Shriver MD, Puts DA (2013). Quantifying the strength and form of sexual selection on men's traits.
Evolution and Human Behavior,
34(5), 334-341.
Abstract:
Quantifying the strength and form of sexual selection on men's traits
Although recent research has increasingly focused on human sexual selection, fundamental questions remain concerning the relative influence of individual traits on success in competition for mates and the mechanisms, form, and direction of these sexual selective pressures. Here, we explore sexual selection on men's traits by ascertaining men's dominance and attractiveness from male and female acquaintances. On a large American university campus, 63 men from two social fraternities provided anthropometric measurements, facial photographs, voice recordings, and reported mating success (number of sexual partners). These men also assessed each other's dominance, and 72 women from two socially affiliated sororities assessed the men's attractiveness. We measured facial masculinity from inter-landmark distances and vocal masculinity from acoustic parameters. We additionally obtained facial and vocal attractiveness and dominance ratings from unfamiliar observers. Results indicate that dominance and the traits associated with it predict men's mating success, but attractiveness and the traits associated with it do not. These findings point to the salience of contest competition on men's mating success in this population. © 2013 the Authors.
Abstract.
Weddle CB, Hunt J, Sakaluk SK (2013). Self-referent phenotype matching and its role in female mate choice in arthropods.
CURRENT ZOOLOGY,
59(2), 239-248.
Author URL.
House CM, Lewis Z, Hodgson DJ, Wedell N, Sharma MD, Hunt J, Hosken DJ (2013). Sexual and natural selection both influence male genital evolution.
PLoS One,
8(5).
Abstract:
Sexual and natural selection both influence male genital evolution.
Rapid and divergent evolution of male genital morphology is a conspicuous and general pattern across internally fertilizing animals. Rapid genital evolution is thought to be the result of sexual selection, and the role of natural selection in genital evolution remains controversial. However, natural and sexual selection are believed to act antagonistically on male genital form. We conducted an experimental evolution study to investigate the combined effects of natural and sexual selection on the genital-arch lobes of male Drosophila simulans. Replicate populations were forced to evolve under lifetime monogamy (relaxed sexual selection) or lifetime polyandry (elevated sexual selection) and two temperature regimes, 25°C (relaxed natural selection) or 27°C (elevated natural selection) in a fully factorial design. We found that natural and sexual selection plus their interaction caused genital evolution. Natural selection caused some aspects of genital form to evolve away from their sexually selected shape, whereas natural and sexual selection operated in the same direction for other shape components. Additionally, sexual and natural selection tended to favour larger genitals. Thus we find that the underlying selection driving genital evolution is complex, does not only involve sexual selection, and that natural selection and sexual selection do not always act antagonistically.
Abstract.
Author URL.
Full text.
Steiger S, Ower GD, Stökl J, Mitchell C, Hunt J, Sakaluk SK (2013). Sexual selection on cuticular hydrocarbons of male sagebrush crickets in the wild.
Proceedings of the Royal Society B: Biological Sciences,
280(1773).
Abstract:
Sexual selection on cuticular hydrocarbons of male sagebrush crickets in the wild
Cuticular hydrocarbons (CHCs) play an essential role in mate recognition in insects but the form and intensity of sexual selection on CHCs has only been evaluated in a handful of studies, and never in a natural population.We quantified sexual selection operating on CHCs in a wild population of sagebrush crickets, a species in which nuptial feeding by females imposes an unambiguous phenotypic marker on males. Multivariate selection analysis revealed a saddle-shaped fitness surface, suggesting a complex interplay between the total abundance of CHCs and specific CHC combinations in their influence on female choice. The fitness surface resulting from two axes of disruptive selection reflected a trade-off between short- and long-chained CHCs, suggesting that males may be sacrificing some level of desiccation resistance in favour of increased attractiveness. There was a significant correlation between male body size and total CHC abundance, suggesting that male CHCs provide females with a reliable cue for maximizing benefits obtained from males. Notwithstanding the conspicuousness of males' acoustic signals, our results suggest that selection imposed on males via female mating preferences may be far more complex than previously appreciated and operating in multiple sensory modalities. © 2013 the Author(s) Published by the Royal Society.
Abstract.
Steiger S, Ower GD, Stökl J, Mitchell C, Hunt J, Sakaluk SK (2013). Sexual selection on cuticular hydrocarbons of male sagebrush crickets in the wild.
Proc Biol Sci,
280(1773).
Abstract:
Sexual selection on cuticular hydrocarbons of male sagebrush crickets in the wild.
Cuticular hydrocarbons (CHCs) play an essential role in mate recognition in insects but the form and intensity of sexual selection on CHCs has only been evaluated in a handful of studies, and never in a natural population. We quantified sexual selection operating on CHCs in a wild population of sagebrush crickets, a species in which nuptial feeding by females imposes an unambiguous phenotypic marker on males. Multivariate selection analysis revealed a saddle-shaped fitness surface, suggesting a complex interplay between the total abundance of CHCs and specific CHC combinations in their influence on female choice. The fitness surface resulting from two axes of disruptive selection reflected a trade-off between short- and long-chained CHCs, suggesting that males may be sacrificing some level of desiccation resistance in favour of increased attractiveness. There was a significant correlation between male body size and total CHC abundance, suggesting that male CHCs provide females with a reliable cue for maximizing benefits obtained from males. Notwithstanding the conspicuousness of males' acoustic signals, our results suggest that selection imposed on males via female mating preferences may be far more complex than previously appreciated and operating in multiple sensory modalities.
Abstract.
Author URL.
Callander S, Kahn AT, Hunt J, Backwell PRY, Jennions MD (2013). The effect of competitors on calling effort and life span in male field crickets.
BEHAVIORAL ECOLOGY,
24(5), 1251-1259.
Author URL.
2012
Sharma MD, Hunt J, Hosken DJ (2012). Antagonistic responses to natural and sexual selection and the sex-specific evolution of cuticular hydrocarbons in Drosophila simulans.
Evolution,
66(3), 665-677.
Abstract:
Antagonistic responses to natural and sexual selection and the sex-specific evolution of cuticular hydrocarbons in Drosophila simulans.
Natural and sexual selection are classically thought to oppose one another, and although there is evidence for this, direct experimental demonstrations of this antagonism are largely lacking. Here, we assessed the effects of sexual and natural selection on the evolution of cuticular hydrocarbons (CHCs), a character subject to both modes of selection, in Drosophila simulans. Natural selection and sexual selection were manipulated in a fully factorial design, and after 27 generations of experimental evolution, the responses of male and female CHCs were assessed. The effects of natural and sexual selection differed greatly across the sexes. The responses of female CHCs were generally small, but CHCs evolved predominantly in the direction of natural selection. For males, profiles evolved via sexual and natural selection, as well as through the interaction between the two, with some male CHC components only evolving in the direction of natural selection when sexual selection was relaxed. These results indicate sex-specific responses to selection, and that sexual and natural selection act antagonistically for at least some combinations of CHCs.
Abstract.
Author URL.
Gershman SN, Mitchell C, Sakaluk SK, Hunt J (2012). Biting off more than you can chew: sexual selection on the free amino acid composition of the spermatophylax in decorated crickets.
Proc Biol Sci,
279(1738), 2531-2538.
Abstract:
Biting off more than you can chew: sexual selection on the free amino acid composition of the spermatophylax in decorated crickets.
Nuptial food gifts function to enhance male fertilization success, but their consumption is not always beneficial to females. In decorated crickets, the spermatophore transferred at mating includes a gelatinous mass, the spermatophylax, which is consumed by females after mating. However, females often discard spermatophylaxes shortly after mating, whereupon they terminate sperm transfer. We hypothesized that females discard gifts based on their assessment of the gift itself, and specifically the composition of free amino acids. We tested this hypothesis by comparing spermatophylaxes discarded by females after mating with those that were destined to be fully consumed, and employed multivariate selection analysis to quantify the strength and form of multivariate sexual selection operating on the free amino acid composition of gifts. The analysis yielded a saddle-shaped fitness surface with two local peaks. Different amino acid profiles appear to elicit continued feeding on the spermatophylax either because they offer the same level of gustatory appeal, or because they differentially affect both the gustatory appeal and texture of the spermatophylax. We conclude that the gustatory response of females to males' nuptial food gifts represents an important avenue of post-copulatory mate choice, imposing significant sexual selection on the free amino acid composition of the spermatophylax.
Abstract.
Author URL.
Weddle CB, Steiger S, Hamaker CG, Ower GD, Mitchell C, Sakaluk SK, Hunt J (2012). Cuticular hydrocarbons as a basis for chemosensory self-referencing in crickets: a potentially universal mechanism facilitating polyandry in insects. Ecology Letters
Ingleby FC, Hosken DJ, Flowers K, Hawkes MF, Lane SM, Rapkin J, Dworkin I, Hunt J (2012). Genotype-by-environment interactions for cuticular hydrocarbon expression in Drosophila simulans. Journal of Evolutionary Biology
Jensen K, Mayntz D, Toft S, Clissold FJ, Hunt J, Raubenheimer D, Simpson SJ (2012). Optimal foraging for specific nutrients in predatory beetles.
Proc Biol Sci,
279(1736), 2212-2218.
Abstract:
Optimal foraging for specific nutrients in predatory beetles.
Evolutionary theory predicts that animals should forage to maximize their fitness, which in predators is traditionally assumed equivalent to maximizing energy intake rather than balancing the intake of specific nutrients. We restricted female predatory ground beetles (Anchomenus dorsalis) to one of a range of diets varying in lipid and protein content, and showed that total egg production peaked at a target intake of both nutrients. Other beetles given a choice to feed from two diets differing only in protein and lipid composition selectively ingested nutrient combinations at this target intake. When restricted to nutritionally imbalanced diets, beetles balanced the over- and under-ingestion of lipid and protein around a nutrient composition that maximized egg production under those constrained circumstances. Selective foraging for specific nutrients in this predator thus maximizes its reproductive performance. Our findings have implications for predator foraging behaviour and in the structuring of ecological communities.
Abstract.
Author URL.
Archer CR, Sakaluk SK, Selman C, Royle NJ, Hunt J (2012). Oxidative stress and the evolution of sex differences in life span and ageing in the decorated cricket, gryllodes sigillatus. Evolution
Weddle CB, Mitchell C, Bay SK, Sakaluk SK, Hunt J (2012). Sex-specific genotype-by-environment interactions for cuticular hydrocarbon expression in decorated crickets, Gryllodes sigillatus: implications for the evolution of signal reliability.
JOURNAL OF EVOLUTIONARY BIOLOGY,
25(10), 2112-2125.
Author URL.
Archer CR, Zajitschek F, Sakaluk SK, Royle NJ, Hunt J (2012). Sexual selection affects the evolution of lifespan and ageing in the decorated cricket Gryllodes sigillatus.
Evolution,
66(10), 3088-3100.
Abstract:
Sexual selection affects the evolution of lifespan and ageing in the decorated cricket Gryllodes sigillatus.
Recent work suggests that sexual selection can influence the evolution of ageing and lifespan by shaping the optimal timing and relative costliness of reproductive effort in the sexes. We used inbred lines of the decorated cricket, Gryllodes sigillatus, to estimate the genetic (co)variance between age-dependent reproductive effort, lifespan, and ageing within and between the sexes. Sexual selection theory predicts that males should die sooner and age more rapidly than females. However, a reversal of this pattern may be favored if reproductive effort increases with age in males but not in females. We found that male calling effort increased with age, whereas female fecundity decreased, and that males lived longer and aged more slowly than females. These divergent life-history strategies were underpinned by a positive genetic correlation between early-life reproductive effort and ageing rate in both sexes, although this relationship was stronger in females. Despite these sex differences in life-history schedules, age-dependent reproductive effort, lifespan, and ageing exhibited strong positive intersexual genetic correlations. This should, in theory, constrain the independent evolution of these traits in the sexes and may promote intralocus sexual conflict. Our study highlights the importance of sexual selection to the evolution of sex differences in ageing and lifespan in G. sigillatus.
Abstract.
Author URL.
Hunt J, Snook RR, Mitchell C, Crudgington HS, Moore AJ (2012). Sexual selection and experimental evolution of chemical signals in Drosophila pseudoobscura.
Journal of Evolutionary Biology,
25(11), 2232-2241.
Abstract:
Sexual selection and experimental evolution of chemical signals in Drosophila pseudoobscura
Our expectations for the evolution of chemical signals in response to sexual selection are uncertain. How are chemical signals elaborated? Does sexual selection result in complexity of the composition or in altered quantities of expression? We addressed this in Drosophila pseudoobscura by examining male and female cuticular hydrocarbons (CHs) after 82 generations of elevated (E) sexual selection or relaxed sexual selection through monogamy (M). The CH profile consisted of 18 different components. We extracted three eigenvectors using principal component analysis that explained 72% of the variation. principal component (PC)1 described the amount of CHs produced, PC2 the trade-off between short- and long-chain CHs and PC3 the trade-off between apparently arbitrary CHs. In both sexes, the amount of CHs produced was greater in flies from the E treatment. PC3 was also higher, indicating that sexual selection also influenced the evolution of CH composition. The sexes differed in all three PCs, indicating substantial sexual dimorphism in this species, although the magnitude of this dimorphism was not increased as a result of our experimental evolution. Collectively, our work provides direct evidence that sexual selection plays an important role in the evolution of CHs in D. pseudoobscura and that both increased quantity and overall composition are targeted. © 2012 the Authors. Journal of Evolutionary Biology © 2012 European Society for Evolutionary Biology.
Abstract.
Hunt J, Snook RR, Mitchell C, Crudgington HS, Moore AJ (2012). Sexual selection and experimental evolution of chemical signals in Drosophila pseudoobscura.
J Evol Biol,
25(11), 2232-2241.
Abstract:
Sexual selection and experimental evolution of chemical signals in Drosophila pseudoobscura.
Our expectations for the evolution of chemical signals in response to sexual selection are uncertain. How are chemical signals elaborated? Does sexual selection result in complexity of the composition or in altered quantities of expression? We addressed this in Drosophila pseudoobscura by examining male and female cuticular hydrocarbons (CHs) after 82 generations of elevated (E) sexual selection or relaxed sexual selection through monogamy (M). The CH profile consisted of 18 different components. We extracted three eigenvectors using principal component analysis that explained 72% of the variation. principal component (PC)1 described the amount of CHs produced, PC2 the trade-off between short- and long-chain CHs and PC3 the trade-off between apparently arbitrary CHs. In both sexes, the amount of CHs produced was greater in flies from the E treatment. PC3 was also higher, indicating that sexual selection also influenced the evolution of CH composition. The sexes differed in all three PCs, indicating substantial sexual dimorphism in this species, although the magnitude of this dimorphism was not increased as a result of our experimental evolution. Collectively, our work provides direct evidence that sexual selection plays an important role in the evolution of CHs in D. pseudoobscura and that both increased quantity and overall composition are targeted.
Abstract.
Author URL.
Drayton JM, Hall MD, Hunt J, Jennions MD (2012). Sexual signaling and immune function in the black field cricket Teleogryllus commodus.
PLoS ONE,
7(7).
Abstract:
Sexual signaling and immune function in the black field cricket Teleogryllus commodus
The immunocompetence handicap hypothesis predicts that male sexual trait expression should be positively correlated with immunocompetence. Here we investigate if immune function in the cricket, Teleogryllus commodus, is related to specific individual components of male sexual signals, as well as to certain multivariate combinations of these components that females most strongly prefer. Male T. commodus produce both advertisement and courtship calls prior to mating. We measured fine-scale structural parameters of both call types and also recorded nightly advertisement calling effort. We then measured two standard indices of immune function: lysozyme-like activity of the haemolymph and haemocyte counts. We found a weak, positive relationship between advertisement calling effort and lysozyme-like activity. There was, however, little evidence that individual structural call components or the net multivariate attractiveness of either call type signalled immune function. The relationships between immunity and sexual signaling did not differ between inbred and outbred males. Our data suggest that it is unlikely that females assess overall male immune function using male calls. © 2012 Drayton et al.
Abstract.
Sharma MD, Mitchell C, Hunt J, Tregenza T, Hosken DJ (2012). The genetics of cuticular hydrocarbon profiles in the Fruit Fly Drosophila simulans.
J Hered,
103(2), 230-239.
Abstract:
The genetics of cuticular hydrocarbon profiles in the Fruit Fly Drosophila simulans.
Female mate choice is one mechanism of sexual selection and, provided there is adequate genetic variation in the male traits that are the target of this selection, they will evolve via female choice. Cuticular hydrocarbons (CHCs) are important in Drosophila mate choice, but relatively little is known about the underlying genetic architecture of CHC profiles in Drosophila simulans. Here, we used gas chromatography-mass spectrometry to investigate patterns of genetic variation in the CHC profiles of male and female D. simulans using isofemale lines. We found substantial genetic variation for CHC profiles and individual CHC components, and individual CHCs were frequently strongly genetically correlated, with a tendency for negative covariance between long- and short-chain CHCs in males. Intersexual genetic covariances were often weak and frequently differed in sign. These findings are novel and significant, highlighting the previously unexplored genetic architecture of CHCs in D. simulans and suggest that this architecture may facilitate sex-specific CHC evolution.
Abstract.
Author URL.
2011
Hunt JE, Scicluna H, McNeil HP (2011). Development and Evaluation of a Mandatory Research Experience in a Medical Education Program: the Independent Learning Project at UNSW.
Medical Science Educator,
21(1), 78-85.
Abstract:
Development and Evaluation of a Mandatory Research Experience in a Medical Education Program: the Independent Learning Project at UNSW
As part of the reform of its undergraduate 6-year medical program, the University of New South Wales developed an in-depth research experience of 24 weeks full-time duration, which all students are required to undertake. Central aims of this Independent Learning Project (ILP) are to develop the generic capability of self-directed learning and critical evaluation, to understand how knowledge is created within a field and its limitations, and to reinforce the scientific basis of medical practice through personal research experience. The ILP is taken in either year 3 or 4 in any area of research relevant to medicine, including biomedical science, public health, and clinical research. Assessment includes supervisor grades and a report in the form of a scientific manuscript. High achieving and motivated students have the option of substituting the ILP period with a formal Bachelor of Science (Medicine) Honours degree, which is 28 weeks in duration with a more rigorous assessment. Currently, this Honours option is limited to the academically best (∼30) students each year. Between 2006 and 2010, 846 students completed an ILP and 159 undertook an Honours project in lieu. At least 64 peer-reviewed manuscripts have been published as a result of ILP projects. Student evaluations are generally positive with 65% of respondents undertaking an ILP in 2009–2010 reporting that they were satisfied with their experience. Motivation, interest, and recognition were the key factors which characterized students who reported satisfaction with their ILP experiences. In open-ended comments, students reported key intellectual outcomes related to research as the highest ranked ‘best aspects’ of their ILP. The most frequent negative comments reflected resistance to the compulsory nature of the ILP, a need for better selection or training of supervisors, and interruption to their clinical learning.
Abstract.
Lewis Z, Wedell N, Hunt J (2011). Evidence for strong intralocus sexual conflict in the Indian meal moth, Plodia interpunctella.
Evolution,
65(7), 2085-2097.
Abstract:
Evidence for strong intralocus sexual conflict in the Indian meal moth, Plodia interpunctella.
Males and females share a genome and express many shared phenotypic traits, which are often selected in opposite directions. This generates intralocus sexual conflict that may constrain trait evolution by preventing the sexes from reaching their optimal phenotype. Furthermore, if present across multiple loci, intralocus sexual conflict can result in a gender load that may diminish the benefits of sexual selection and help maintain genetic variation for fitness. Despite the importance of intralocus sexual conflict, surprisingly few empirical studies conclusively demonstrate its operation. We show that the pattern of multivariate selection acting on three sexually dimorphic life-history traits (development time, body size, and longevity) in the Indian meal moth, Plodia interpunctella, is opposing for the sexes. Moreover, we combined our estimates of selection with the additive genetic variance-covariance matrix (G) to predict the evolutionary response of the life-history traits in the sexes and showed that the angle between the vector of responses and the vector of sexually antagonistic selection was almost orthogonal at 84.70°. Thus, G biases the predicted response of life-history traits in the sexes away from the direction of sexually antagonistic selection, confirming the presence of strong intralocus sexual conflict in this species. Despite this, sexual dimorphism has evolved in all of the life-history traits examined suggesting that mechanism(s) have evolved to resolve this conflict and allow the sexes to reach their life-history optima. We argue that intralocus sexual conflict is likely to play an important role in the evolution of divergent life-history strategies between the sexes in this species.
Abstract.
Author URL.
Okada K, Pitchers WR, Sharma MD, Hunt J, Hosken DJ (2011). Longevity, calling effort, and metabolic rate in two populations of cricket.
Behavioral Ecology and Sociobiology,
65(9), 1773-1778.
Abstract:
Longevity, calling effort, and metabolic rate in two populations of cricket
Intraspecific variation in a resting metabolic rate (RMR) is likely to be an important determinant of energetic-resource use and may influence the resources subsequently available for allocation to traits not directly associated with somatic maintenance. The influence of RMR on resource availability could be especially important for condition-dependent sexual traits, such as cricket calls, that are themselves energetically costly to produce. RMR may also be associated with longevity, either negatively because individuals with a high RMR burn resources faster and die young, or positively as individuals with high RMR are more able to accrue resources to fuel survival. Additionally, the associations between RMR and other characters may vary across populations if differential selection or drift shapes these traits. Here we tested for differences in RMR, body mass, calling effort, and longevity in two populations of cricket Gryllodes sigillatus and then evaluated the potential influence of RMR on calling and longevity. We find that RMR, calling effort, and longevity varied across populations, but mass did not. Controlling for population and mass, RMR was not significantly associated with calling effort, but was negatively associated with longevity. These findings suggest that male crickets that live fast die young. © 2011 Springer-Verlag.
Abstract.
South SH, House CM, Moore AJ, Simpson SJ, Hunt J (2011). Male cockroaches prefer a high carbohydrate diet that makes them more attractive to females: implications for the study of condition dependence.
Evolution,
65(6), 1594-1606.
Abstract:
Male cockroaches prefer a high carbohydrate diet that makes them more attractive to females: implications for the study of condition dependence.
Sexual selection is a major force driving the evolution of elaborate male sexual traits. Handicap models of sexual selection predict that male sexual traits should covary positively with condition, making them reliable indicators of male quality. However, most studies have either manipulated condition through varying diet quantity and/or caloric content without knowledge of specific nutrient effects or have correlated proxies of condition with sexual trait expression. We used nutritional geometry to quantify protein and carbohydrate intake by male cockroaches, Nauphoeta cinerea, and related this to sex pheromone expression, attractiveness, and dominance status. We found that carbohydrate, but not protein, intake is related to male sex pheromone expression and attractiveness but not dominance status. Additionally, we related two condition proxies (weight gain and lipid reserves) to protein and carbohydrate acquisition. Weight gain increased with the intake of both nutrients, whereas lipid reserves only increased with carbohydrate intake. Importantly, lipid accumulation was not as responsive to carbohydrate intake as attractiveness and thus was a less-accurate condition proxy. Moreover, males preferentially consumed high carbohydrate diets with little regard for protein content suggesting that they actively increase their carbohydrate intake thereby maximizing their reproductive fitness by being attractive.
Abstract.
Author URL.
House CM, Simmons LW, Kotiaho JS, Tomkins JL, Hunt J (2011). Sex ratio bias in the dung beetle Onthophagus taurus: Adaptive allocation or sex-specific offspring mortality?.
Evolutionary Ecology,
25(2), 363-372.
Abstract:
Sex ratio bias in the dung beetle Onthophagus taurus: Adaptive allocation or sex-specific offspring mortality?
Sex allocation theory predicts that females should adjust the sex of their offspring when the fitness returns of one sex are higher than the other. However, biased sex ratios may also arise if mortality differs between the sexes. Here, we examine whether offspring sex ratio bias in the dung beetle, Onthophagus taurus, represents adaptive sex allocation by females or is due to sex-specific mortality. First, we re-analyze an existing data set to show that females produce an excess of daughters when mating to smaller, less attractive males and near equal sex ratio with large, more attractive males. We show, that this results from females adjusting larval provisions after mating to males of variable attractiveness which in turn influences the likelihood that sons die during development. Second, we conduct a manipulative experiment varying the quantity and quality of larval provisions and show that the mortality of sons increased when larval provisions were reduced. Collectively, our work demonstrates that offspring mortality is contingent on the amount of resources provisioned by females and that sons have greater nutritional demands than daughters during development, leading to higher mortality. Our results therefore demonstrate the importance of considering sex-specific offspring mortality in studies of sex ratio evolution. © 2010 Springer Science+Business Media B.V.
Abstract.
Hunt J, House C (2011). The Evolution of Parental Care in the Onthophagine Dung Beetles. In (Ed) Ecology and Evolution of Dung Beetles, 152-176.
Hunt J, House CM (2011). The evolution of parental care in dung beetles. In Simmons LW, Ridsdill-Smith J (Eds.) Dung Beetle Ecology and Evolution.
Gay L, Brown E, Tregenza T, Pincheira-Donoso D, Eady PE, Vasudev R, Hunt J, Hosken DJ (2011). The genetic architecture of sexual conflict: male harm and female resistance in Callosobruchus maculatus.
J Evol Biol,
24(2), 449-456.
Abstract:
The genetic architecture of sexual conflict: male harm and female resistance in Callosobruchus maculatus.
Males harm females during mating in a range of species. This harm is thought to evolve because it is directly or indirectly beneficial to the male, despite being costly to his mate. The resulting sexually antagonistic selection can cause sexual arms races. For sexually antagonistic co-evolution to occur, there must be genetic variation for traits involved in female harming and susceptibility to harm, but even then intersexual genetic correlations could facilitate or impede sexual co-evolution. Male Callosobruchus maculatus harm their mates during copulation by damaging the female's reproductive tract. However, there have been no investigations of the genetic variation in damage or in female susceptibility to damage, nor has the genetic covariance between these characters been assessed. Here, we use a full-sib/half-sib breeding design to show that male damage is heritable, whereas female susceptibility to damage is much less so. There is also a substantial positive genetic correlation between the two, suggesting that selection favouring damaging males will increase the prevalence of susceptible females. We also provide evidence consistent with intralocus sexual conflict in this species.
Abstract.
Author URL.
Hunt J, Hodgson D (2011). What is fitness and how do we measure it?. In Westneat DF, Fox CW (Eds.) Evolutionary Behavioural Ecology, Oxford University Press, 46-71.
2010
Narraway C, Hunt J, Wedell N, Hosken DJ (2010). Genotype by envirnment interactions for female preference. Journal of Evolutionary Biology, 23, 2550-2557.
Gershman SN, Barnett CA, Pettinger AM, Weddle CB, Hunt J, Sakaluk SK (2010). Give 'til it hurts: Trade-offs between immunity and male reproductive effort in the decorated cricket, Gryllodes sigillatus.
Journal of Evolutionary Biology,
23(4), 829-839.
Abstract:
Give 'til it hurts: Trade-offs between immunity and male reproductive effort in the decorated cricket, Gryllodes sigillatus
Trade-offs between life-history variables can be manifested at either the phenotypic or genetic level, with vastly different evolutionary consequences. Here, we examined whether male decorated crickets (. Gryllodes sigillatus) from eight inbred lines and the outbred founder population from which they were derived, trade-off immune effort [lytic activity, phenoloxidase (PO) activity or encapsulation] to produce spermatophylaxes: costly nuptial food gifts essential for successful sperm transfer. Canonical correlation analysis of the outbred population revealed a trade-off between spermatophylax mass and lytic activity. Analysis of our inbred lines, however, revealed that although PO activity, encapsulation, body mass, spermatophylax mass and ampulla (sperm capsule) mass were all highly heritable, lytic activity was not, and there was, therefore, no negative genetic correlation between lytic activity and spermatophylax mass. Thus, males showed a phenotypic but not a genetic trade-off between spermatophylax mass and lytic activity, suggesting that this trade-off is mediated largely by environmental factors. © 2010 the Authors. Journal Compilation © 2010 European Society for Evolutionary Biology.
Abstract.
Gershman SN, Pettinger AM, Weddle CB, Hunt J, Barnett CA (2010). Inbred decorated crickets exhibit higher immunity than outbred individuals. Heredity
Gershman SN, Barnett CA, Pettinger AM, Weddle CB, Hunt J, Sakaluk SK (2010). Inbred decorated crickets exhibit higher measures of macroparasitic immunity than outbred individuals.
Heredity,
105(3), 282-289.
Abstract:
Inbred decorated crickets exhibit higher measures of macroparasitic immunity than outbred individuals
Inbreeding is assumed to have negative effects on fitness, including the reduced ability to withstand immune challenges. We examined the immunological consequences of inbreeding in decorated crickets, Gryllodes sigillatus, by comparing lytic activity, phenoloxidase (PO) activity, and encapsulation ability of crickets from eight inbred lines with that of crickets from the outbred founder population. Surprisingly, crickets from inbred lines had a greater encapsulation ability compared with crickets from the outbred population. We suggest that because inbred crickets have reduced reproductive effort, they may, therefore, have the option of devoting more resources to this form of immunity than outbred individuals. We also found that both inbred and outbred females had higher immunity than males in PO activity and implant darkness. This result supports the hypothesis that females should devote more effort to somatic maintenance and immunity than males. PO activity and implant darkness were heritable in both males and females, but lytic activity was only heritable in females. Males and females differed in the heritability of, and genetic correlations among, immune traits, suggesting that differences in selective pressures on males and females may have resulted in a sexual conflict over optimal immune trait values. © 2010 Macmillan Publishers Limited all rights reserved.
Abstract.
Drayton JM, Milner RNC, Hunt J, Jennions MD (2010). Inbreeding and advertisement calling in the cricket Teleogryllus commodus: laboratory and field experiments.
Evolution,
64(10), 3069-3083.
Abstract:
Inbreeding and advertisement calling in the cricket Teleogryllus commodus: laboratory and field experiments.
If sexually selected traits reveal a male's heterozygosity or condition to females, then such traits should exhibit declines with inbreeding. We tested this by examining the effect of inbreeding on advertisement calling in male crickets Teleogryllus commodus. We investigated the effect of one generation of full-sibling mating on calling effort and fine-scale call structure. Inbreeding reduced calling effort but had no effect on call structure. We then compared the attractiveness of inbred and outbred calls in the field by monitoring how many wild females were attracted to each call type. From the field data, we conducted a selection analysis to identify the major axes of linear and nonlinear multivariate sexual selection on call structure. A comparison of multivariate attractiveness of inbred and outbred calls along each major axis of selection revealed no difference in attractiveness. Our results suggest that inbred male calls have a fine-scale structure that is no less attractive to females than that of outbred calls. However, because inbred males call less often, and female T. commodus prefer males with a higher calling effort, inbred males will suffer reductions in mating success. Females who base mate choice on call rate are therefore using a signal correlated with male heterozygosity and/or condition.
Abstract.
Author URL.
House C, Roth C, Hunt J, Kover PX (2010). Paternal effects in Arabidopsis indicate that offspring can influence their own size.
PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES,
277(1695), 2885-2893.
Author URL.
Mallitt KL, Bonser SP, Hunt J (2010). The plasticity of phenotypic integration in response to light and water availability in the pepper grass, Lepidium bonariense.
EVOLUTIONARY ECOLOGY,
24(6), 1321-1337.
Author URL.
Ingleby FC, Hunt J, Hosken DJ (2010). The role of genotype-by-environment interactions in sexual selection.
J Evol Biol,
23(10), 2031-2045.
Abstract:
The role of genotype-by-environment interactions in sexual selection.
Genotype-by-environment interactions (GxEs) in naturally selected traits have been extensively studied, but the impact of GxEs on sexual selection has only recently begun to receive attention. Here, we review recent models and consider how GxEs might affect the evolution of sexual traits through influencing sexual signal reliability and also how GxEs may influence variation in sexually selected traits and the process of reproductive isolation. We then assess the current empirical literature on GxEs in sexual selection and conclude by highlighting areas that need additional work. Research on GxEs and sexual selection is an important new area of study for the discipline, which has largely focused on relatively simple mate choice/competition scenarios to date. Investigators now need to apply this knowledge to more complex, but realistic, situations, to more fully explore the evolution of sexual traits, and in this review we suggest potentially useful directions for future research.
Abstract.
Author URL.
2009
Zajitschek F, Hunt J, Jennions MD, Hall MD, Brooks RC (2009). Effects of juvenile and adult diet on ageing and reproductive effort of male and female black field crickets, Teleogryllus commodus.
Functional Ecology,
23(3), 602-611.
Abstract:
Effects of juvenile and adult diet on ageing and reproductive effort of male and female black field crickets, Teleogryllus commodus
How and when resources are allocated to reproduction is expected to differ between the sexes, potentially generating differences in how males and females age. For this reason, acquisition of resources should be an important determinant of both age-dependent reproductive effort and of deteriorative ageing (i.e. senescence). We used black field crickets, Teleogryllus commodus, to test whether differences in diet quality of juveniles and adults determine sex-specific resource allocation to reproduction and whether there are any subsequent effects on ageing. We show that ageing does not depend on nymph diet. There was, however, a significant difference in the rates of actuarial ageing for males and females. Females showed reproductive ageing, whereas male reproductive effort plateaus or continues to increase with age. 4. These results highlight the link between diet, reproduction and ageing and show that differences in resource utilization between the sexes can lead to different patterns of ageing. This is likely to have profound effects on how life-histories evolve in the sexes. © 2008 British Ecological Society.
Abstract.
Simmons LW, House CM, Hunt J, García-González F (2009). Evolutionary response to sexual selection in male genital morphology.
Curr Biol,
19(17), 1442-1446.
Abstract:
Evolutionary response to sexual selection in male genital morphology.
Male genital morphology is characterized by two striking and general patterns of morphological variation: rapid evolutionary divergence in shape and complexity, and relatively low scaling relationships with body size. These patterns of variation have been ascribed to the action of sexual selection. Among species, monogamous taxa tend to have relatively less complex male genital morphology than do polygamous taxa. However, although variation in male genital morphology can be associated with variation in mating and fertilization success, there is no direct evidence that sexual selection generates the evolutionary changes in male genital shape that underlie observed macroevolutionary patterns. Moreover, the hypothesis that sexual selection acts to reduce the scaling relationship between body and genital size is based entirely on the theoretical argument that male genitalia should be selected to provide an appropriate mechanical and/or stimulatory fit to the most commonly encountered female genitalia. Here, using the dung beetle Onthophagus taurus, we combine the power of experimental evolution with multivariate selection and quantitative genetic analyses to provide the most comprehensive evidence available of the form and evolutionary consequences of sexual selection acting on male genital morphology.
Abstract.
Author URL.
Hunt J, Breuker CJ, Sadowski JA, Moore AJ (2009). Male-male competition, female mate choice and their interaction: determining total sexual selection.
J Evol Biol,
22(1), 13-26.
Abstract:
Male-male competition, female mate choice and their interaction: determining total sexual selection.
Empirical studies of sexual selection typically focus on one of the two mechanisms of sexual selection without integrating these into a description of total sexual selection, or study total sexual selection without quantifying the contributions of all of the mechanisms of sexual selection. However, this can provide an incomplete or misleading view of how sexually selected traits evolve if the mechanisms of sexual selection are opposing or differ in form. Here, we take a two-fold approach to advocate a direction for future studies of sexual selection. We first show how a quantitative partitioning and examination of sexual selection mechanisms can inform by identifying illustrative studies that describe both male-male competition and female mate choice acting on the same trait. In our sample, the most common trait where this occurred was body size, and selection was typically linear. We found that male-male competition and female mate choice can be reinforcing or opposing, although the former is most common in the literature. The mechanisms of sexual selection can occur simultaneously or sequentially, and we found they were more likely to be opposing when the mechanisms operated sequentially. The degree and timing that these mechanisms interact have important implications for the operation of sexual selection and needs to be considered in designing studies. Our examples highlight where empirical data are needed. We especially lack standardized measures of the form and strength of selection imposed by each mechanism of sexual selection and how they combine to determine total sexual selection. Secondly, using quantitative genetic principles, we outline how the selection imposed by individual mechanisms can be measured and combined to estimate the total strength and form of sexual selection. We discuss the evolutionary consequences of combining the mechanisms of sexual selection and interpreting total sexual selection. We suggest how this approach may result in empirical progress in the field of sexual selection.
Abstract.
Author URL.
Archer CR, Royle N, South S, Selman C, Hunt J (2009). Nutritional geometry provides food for thought.
J Gerontol a Biol Sci Med Sci,
64(9), 956-959.
Abstract:
Nutritional geometry provides food for thought.
Dietary Restriction extends lifespan in a diverse range of animals, but this often comes at a cost to reproduction. While a number of molecular pathways integral to these relationships have been characterised, we still do not fully understand whether restriction of specific nutrients or calories is responsible. Two recent studies on insects have offered novel insights into this longstanding issue via the application of Nutritional Geometry. This technique promises to significantly advance our understanding of how nutrition influences reproduction and longevity.
Abstract.
Author URL.
Edvardson M, Hunt J, Moore AJ, Moore PJ (2009). Quantitative genetic variation in the control of apoptosis associated with midlife fertility loss. Heredity, 103, 217-222.
Barrett ELB, Hunt J, Moore AJ, Moore PJ (2009). Separate and combined effects of nutrition during juvenile and sexual development on female life-history trajectories: the thrifty phenotype in a cockroach.
Proc Biol Sci,
276(1671), 3257-3264.
Abstract:
Separate and combined effects of nutrition during juvenile and sexual development on female life-history trajectories: the thrifty phenotype in a cockroach.
We have yet to understand fully how conditions during different periods of development interact to influence life-history structure. Can the negative effects of poor juvenile nutrition be overcome by a good adult diet, or are life-history strategies set by early experience? Here, we tested the influence and interaction of different nutritional quality during juvenile and sexual development on female resource allocation physiology, life history and courtship behaviour in the cockroach, Nauphoeta cinerea. Nymphs were raised on either a good-quality or poor-quality diet. After adult eclosion, females were either switched to the opposite diet or remained on their original diet. We assessed mating behaviour and lifetime reproductive success for half of the females from each treatment. We evaluated reproductive investment, somatic investment and resource reallocation from reproduction to the soma via oocyte apoptosis in the remaining females. We found that poor juvenile conditions resulted in a fat phenotype with slow juvenile growth and short reproductive lifespan that could not be retrieved with a change in diet. Good juvenile conditions resulted in the converse, but again fixed, phenotype in adulthood. Thus, juvenile nutrition sets adult patterns of resource allocation.
Abstract.
Author URL.
2008
Hall MD, Bussière LF, Hunt J, Brooks R (2008). Experimental evidence that sexual conflict influences the opportunity, form and intensity of sexual selection.
Evolution,
62(9), 2305-2315.
Abstract:
Experimental evidence that sexual conflict influences the opportunity, form and intensity of sexual selection.
Sexual interactions are often rife with conflict. Conflict between members of the same sex over opportunities to mate has long been understood to effect evolution via sexual selection. Although conflict between males and females is now understood to be widespread, such conflict is seldom considered in the same light as a general agent of sexual selection. Any interaction between males or females that generates variation in fitness, whether due to conflict, competition or mate choice, can potentially influence sexual selection acting on a range of male traits. Here we seek to address a lack of direct experimental evidence for how sexual conflict influences sexual selection more broadly. We manipulate a major source of sexual conflict in the black field cricket, Teleogryllus commodus, and quantify the resulting changes in the nature of sexual selection using formal selection analysis to statistically compare multivariate fitness surfaces. In T. commodus, sexual conflict occurs over the attachment time of an external spermatophore. By experimentally manipulating the ability of males and females to influence spermatophore attachment, we found that sexual conflict significantly influences the opportunity, form, and intensity of sexual selection on male courtship call and body size. When males were able to harass females, the opportunity for selection was smaller, the form of selection changed, and sexual selection was weaker. We discuss the broader evolutionary implications of these findings, including the contributions of sexual conflict to fluctuating sexual selection and the maintenance of additive genetic variation.
Abstract.
Author URL.
Hunt, J. Moore, P.J. Moore, A.J. (2008). Female agreement over male attractiveness is not affected by cost of mating with experienced males. Behavioral Ecology
2007
Jennions MD, Drayton JM, Brooks R, Hunt J (2007). Do female black field crickets Teleogryllus commodus benefit from polyandry?.
Journal of Evolutionary Biology,
20(4), 1469-1477.
Abstract:
Do female black field crickets Teleogryllus commodus benefit from polyandry?
Female insects that mate multiply tend to have increased lifetime fitness, apparently because of greater access to male-derived resources (e.g. sperm, nuptial gifts) that elevate fertility/fecundity. Experiments that standardize the number of matings per female also show that polyandry can improve aspects of offspring performance, most notably early embryo survival (egg hatching success). This improvement is widely attributed to genetic benefits which would arise if polyandrous females skew paternity to produce fitter offspring. In two separate experiments with field crickets (Teleogryllus commodus) polyandrous females (two, three or four mates) did not have higher egg hatching success than monandrous females (effect sizes: r = 0.03 and 0.08 for the respective experiments), which is consistent with our finding of no sire effect on hatching success. Polyandry also had no effect on post-hatching offspring survival. Polyandrous females' offspring took significantly longer to mature but their sons were not heavier and their daughters were actually significantly smaller than those of monandrous females. Finally, after controlling for relative male size, monandrous females' sons were more successful when directly competing for a mate. © 2007 the Authors.
Abstract.
House CM, Hunt J, Hosken DJ (2007). Evolution: lending a helping hand in sperm competition?.
Curr Biol,
17(3), R90-R93.
Abstract:
Evolution: lending a helping hand in sperm competition?
Most females mate with many males. This can be costly, but the benefits to females are often unclear. A new study raises the possibility that females could benefit through an unconventional genetic pathway, while also showing that males can inadvertently increase rival males' fitness in surprising ways.
Abstract.
Author URL.
McGowan A, Wright LI, Hunt J (2007). Inbreeding and population dynamics: implications for conservation strategies.
ANIMAL CONSERVATION,
10(3), 284-285.
Author URL.
Zajitschek F, Hunt J, Zajitschek SRK, Jennions MD, Brooks R (2007). No intra-locus sexual conflict over reproductive fitness or ageing in field crickets.
PLoS One,
2(1).
Abstract:
No intra-locus sexual conflict over reproductive fitness or ageing in field crickets.
Differences in the ways in which males and females maximize evolutionary fitness can lead to intra-locus sexual conflict in which genes delivering fitness benefits to one sex are costly when expressed in the other. Trade-offs between current reproductive effort and future reproduction and survival are fundamental to the evolutionary biology of ageing. This leads to the prediction that sex differences in the optimization of age-dependent reproductive effort may generate intra-locus sexual conflict over ageing rates. Here we test for intra-locus sexual conflict over age-dependent reproductive effort and longevity in the black field cricket, Teleogryllus commodus. Using a half-sib breeding design, we show that the most important components of male and female reproductive effort (male calling effort and the number of eggs laid by females) were positively genetically correlated, especially in early adulthood. However, the genetic relationships between longevity and reproductive effort were different for males and females, leading to low genetic covariation between male and female longevity. The apparent absence of intra-locus sexual conflict over ageing suggests that male and female longevity can evolve largely independently of one another.
Abstract.
Author URL.
Blows, M.W. Zajitschek, F. Jennions, M.D. (2007). Reconciling strong stabilizing selection with the maintenance of genetic variation in a natural population of the black field crickets, Teleogryllus commodus. Genetics, 177, 875-880.
Drayton JM, Hunt J, Brooks R, Jennions MD (2007). Sounds different: Inbreeding depression in sexually selected traits in the cricket Teleogryllus commodus.
Journal of Evolutionary Biology,
20(3), 1138-1147.
Abstract:
Sounds different: Inbreeding depression in sexually selected traits in the cricket Teleogryllus commodus
If male sexual signalling is honest because it captures genetic variation in condition then traits that are important mate choice cues should be disproportionately affected by inbreeding relative to other traits. To test this, we investigated the effect of brother-sister mating on advertisement calling by male field crickets Teleogryllus commodus. We quantified the effect of one generation of inbreeding on nightly calling effort and five finer-scale aspects of call structure that have been shown to influence attractiveness. We also quantified inbreeding depression on six life history traits and one morphological trait. Inbreeding significantly reduced hatching success, nymph survival and adult lifespan but had no detectable effect on hatching rate, developmental rate or adult body mass. The effect of inbreeding on sexually selected traits was equivocal. There was no decline in calling effort (seconds of sound production/night) by inbred males, but there were highly significant changes in three of five finer-scale call parameters. Sexually selected traits clearly vary in their susceptibility to inbreeding depression. © 2007 the Authors.
Abstract.
House CM, Hunt J, Moore AJ (2007). Sperm competition, alternative mating tactics and context-dependent fertilization success in the burying beetle, Nicrophorus vespilloides.
Proc Biol Sci,
274(1615), 1309-1315.
Abstract:
Sperm competition, alternative mating tactics and context-dependent fertilization success in the burying beetle, Nicrophorus vespilloides.
Fertilization success in sperm competition is often determined by laboratory estimates of the proportion of offspring sired by the first (P1) or second (P2) male that mates. However, inferences from such data about how sexual selection acts on male traits in nature may be misleading if fertilization success depends on the biological context in which it is measured. We used the sterile male technique to examine the paternity of the same male in two mating contexts in the burying beetle, Nicrophorus vespilloides, a species where males have alternative mating strategies based on the presence or absence of resources. We found no congruence in the paternity achieved by a given male when mating under different social conditions. P2 estimates were extremely variable under both conditions. Body size was unrelated to success in sperm competition away from a carcass but, most probably through pre-copulatory male-male competition, influenced fertilization success on a carcass. The contribution of sperm competition is therefore dependent on the conditions under which it is measured. We discuss our findings in relation to sperm competition theory and highlight the need to consider biological context in order to link copulation and fertilization success for competing males.
Abstract.
Author URL.
Hunt J, Wolf JB, Moore AJ (2007). The biology of multivariate evolution.
J Evol Biol,
20(1), 24-27.
Author URL.
2006
Hunt JC, Brooks R, Jennions MD, Spyrou N (2006). Artificial selection on male longevity influences age-dependent reproductive effort in the black field cricket Teleogryllus commodus. The American Naturalist, 168(3), E72-E86.
Lessells CM, Bennett ATD, Birkhead TR, Colegrave N, Dall SRX, Harvey PH, Hatchwell B, Hosken DJ, Hunt J, Moore AJ, et al (2006). Debating sexual selection and mating strategies.
SCIENCE,
312(5774), 689-690.
Author URL.
Head ML, Hunt J, Brooks R (2006). Genetic association between male attractiveness and female differential allocation. Biology Letters, 2, 341-344.
Hunt, J. Jennions, D. Brooks, R. (2006). Sexual conflict and Cryptic female choice in the black field cricket, Teleogryllus Commodus. Evolution, 60(4), 792-800.
Lindholm AK, Hunt J, Brooks R (2006). Where do all the maternal effects go? Variation in offspring body size through ontogeny in the live-bearing fish Poecilia parae.
Biol Lett,
2(4), 586-589.
Abstract:
Where do all the maternal effects go? Variation in offspring body size through ontogeny in the live-bearing fish Poecilia parae.
Maternal effects are an important source of adaptive variation, but little is known about how they vary throughout ontogeny. We estimate the contribution of maternal effects, sire genetic and environmental variation to offspring body size from birth until 1 year of age in the live-bearing fish Poecilia parae. In both the sexes, maternal effects on body size were initially high in juveniles, and then declined to zero at sexual maturity. In sons, this was accompanied by a sharp rise in sire genetic variance, consistent with the expression of Y-linked loci affecting male size. In daughters, all variance components decreased with time, consistent with compensatory growth. There were significant negative among-dam correlations between early body size and the timing of sexual maturity in both sons and daughters. However, there was no relationship between early life maternal effects and adult longevity, suggesting that maternal effects, although important early in life, may not always influence late life-history traits.
Abstract.
Author URL.
2005
Hunt, J. Jennions, M.D. (2005). Complex multivariate sexual selection on male acoustic signalling in a wild population of Teleogryllus commodus. American Naturalist
Hunt, J. Simmons, L.W. (2005). Evolution of sexual dimorphism and male dimorphism in the expression of beetle horns: phylogenetic evidence for modularity, evolutionary lability, and constraint. American Naturalist, 166, S42-S68.
Brooks R, Hunt J, Blows MW, Smith MJ, Bussiere LF, Jennions MD (2005). Experimental evidence for multivariate stabilizing selection. Evolution, 59, 871-880.
Hunt J, Brooks R, Jennions MD (2005). Female mate choice as a condition-dependent life-history trait.
Am Nat,
166(1), 79-92.
Abstract:
Female mate choice as a condition-dependent life-history trait.
The acquisition of resources is an important determinant of patterns of variation in and covariation among traits that are costly to produce and are dependent on condition for their expression. However, the extent to which variation in female mate choice behavior is condition dependent, and how this is related to other life-history traits, remains largely unknown. We manipulated the acquisition of dietary protein in the black field cricket, Teleogryllus commodus, and measured the effects of this on several important life-history traits and on female mate choice behavior. Females reared on a high-protein diet developed faster, were heavier at eclosion, and lived longer than females reared on a low-protein diet. Two lines of evidence suggest that female mate choice behavior in T. commodus is condition dependent. First, females reared on the high-protein diet were more sexually responsive and expressed stronger linear and quadratic preference functions for call rate and dominant frequency, respectively. Second, within treatments, females that developed faster were lighter, generally less sexually responsive, and, in the high-protein-diet treatment, expressed weaker preferences than slower-developing females. Collectively, our findings suggest an important role for resource acquisition in generating variation in mate choice behavior.
Abstract.
Author URL.
Jennions, M.D. Hunt, J. (2005). Fighting success and attractiveness as predictors of male mating success in the black field cricket Teleogryllus commodus: the effectiveness of no-choice tests. Behavioral Ecology and Sociobiology, 58, 1-8.
Hunt, J. Jennions, M.D. (2005). Male attractiveness covaries with fighting ability but not prior fight outcome in house crickets. Behavioral Ecology, 16, 196-200.
Head ML, Hunt J, Jennions MD, Brooks R (2005). The indirect benefits of mating with attractive males outweigh the direct costs.
PLoS Biology,
3(2), 0289-0294.
Abstract:
The indirect benefits of mating with attractive males outweigh the direct costs
The fitness consequences of mate choice are a source of ongoing debate in evolutionary biology. Recent theory predicts that indirect benefits of female choice due to offspring inheriting superior genes are likely to be negated when there are direct costs associated with choice, including any costs of mating with attractive males. To estimate the fitness consequences of mating with males of varying attractiveness, we housed female house crickets, Acheta domesticus, with either attractive or unattractive males and measured a variety of direct and indirect fitness components. These fitness components were combined to give relative estimates of the number of grandchildren produced and the intrinsic rate of increase (relative net fitness). We found that females mated to attractive males incur a substantial survival cost. However, these costs are cancelled out and may be outweighed by the benefits of having offspring with elevated fitness. This benefit is due predominantly, but not exclusively, to the effect of an increase in sons' attractiveness. Our results suggest that the direct costs that females experience when mating with attractive males can be outweighed by indirect benefits. They also reveal the value of estimating the net fitness consequences of a mating strategy by including measures of offspring quality in estimates of fitness. Copyright: © 2005 Head et al.
Abstract.
Hunt, J. Jennions, M.D. (2005). The indirect benefits of mating with attractive males outweigh the direct costs. Public Library of Science, Biology, 3, 279-284.
2004
Hunt J, Brooks R, Jennions MD, Smith MJ, Bentsen CL, Bussière LF (2004). High-quality male field crickets invest heavily in sexual display but die young.
Nature,
432(7020), 1024-1027.
Abstract:
High-quality male field crickets invest heavily in sexual display but die young.
Only high-quality males can bear the costs of an extreme sexual display. As a consequence, such males are not only more attractive, but they often live longer than average. Recent theory predicts, however, that high-quality males should sometimes invest so heavily in sexual displays that they die sooner than lower quality males. We manipulated the phenotypic quality of field crickets, Teleogryllus commodus, by altering the protein content of their diet. Here we show that nymphs and adult females reared on a high-protein diet lived longer than those on a low-protein diet. In contrast, adult males reared on a high-protein diet died sooner than those on low-protein diets because they invested more energy in calling during early adulthood. Our findings uphold the theoretical prediction that the relationship between longevity and sexual advertisement may be dynamic (that is, either positive or negative), depending on local conditions such as resource availability. Moreover, they caution the use of longevity as a proxy for fitness in sexual selection studies, and suggest avenues for future research on the relationship between sexual attractiveness and ageing.
Abstract.
Author URL.
Hunt, J. Graham, R. (2004). No evidence for inbreeding avoidance through post-copulatory mechanisms in the black field cricket Teleogryllus commodus. Evolution, 58, 2472-2477.
Simmons, L.W. (2004). Optimal maternal investment in the dung beetle Onthophagus taurus. Behavioral Ecology and Sociobiology, 42, 447-451.
Brooks, R. (2004). The mother-in-law effect. Proceedings of the Royal Society Series B. Biology Letters, Supplement, 271, S61-S63.
Hunt J, Bussière LF, Jennions MD, Brooks R (2004). What is genetic quality?.
Trends in Ecology and Evolution,
19(6), 329-333.
Abstract:
What is genetic quality?
Mate choice is favored by indirect selection if choosy females mate with males of high genetic quality. We believe, however, that testing hypotheses about indirect selection has been constrained by how we conceptualize and therefore empirically measure male genetic quality. Here, we argue that genetic quality is the breeding value of an individual for total fitness. We can therefore learn little about genetic quality from measures of only a few fitness components. We explain breeding value for total fitness, drawing on concepts from life-history theory and quantitative genetics, and suggest how approaches incorporating these insights might result in empirical progress.
Abstract.
2003
Kotiaho JS, Simmons LW, Hunt J, Tomkins JL (2003). Males influence maternal effects that promote sexual selection: a quantitative genetic experiment with dung beetles Onthophagus taurus.
Am Nat,
161(6), 852-859.
Abstract:
Males influence maternal effects that promote sexual selection: a quantitative genetic experiment with dung beetles Onthophagus taurus.
Recently, doubt has been cast on studies supporting good genes sexual selection by the suggestion that observed genetic benefits for offspring may be confounded by differential maternal allocation. In traditional analyses, observed genetic sire effects on offspring phenotype may result from females allocating more resources to the offspring of attractive males. However, maternal effects such as differential allocation may represent a mechanism promoting genetic sire effects, rather than an alternative to them. Here we report results from an experiment on the horned dung beetle Onthophagus taurus, in which we directly compare genetic sire effects with maternal effects that are dependent on sire phenotype. We found strong evidence that mothers provide more resources to offspring when mated with large-horned males. There were significant heritabilities for both horn length and body size, but when differential maternal effects were controlled, the observed estimates of genetic variance were greatly reduced. Our experiment provides evidence that differential maternal effects may amplify genetic effects on offspring traits that are closely related to fitness. Thus, our results may partly explain the relatively high coefficients of additive genetic variation observed in fitness-related traits and provide empirical support for the theoretical argument that maternal effects can play an important role in evolution.
Abstract.
Author URL.
Møller, A.P. Hunt, J. (2003). Meta-analysis can "fail": reply to Kotiaho & Tomkins. Oikos, 104, 191-193.
Bussiere, L. Jennions, M.D. (2003). Sinister strategies succeed at the Cricket World Cup. Proceedings of the Royal Society Series B. Biology Letters, Supplement, 271, S64-S66.
2002
Simmons, L.W. Kotiaho, J.S. (2002). A cost of maternal care in the dung beetle Onthophagus taurus. Journal of Evolutionary Biology, 15, 57-64.
Simmons, L.W. (2002). Behavioural dynamics of biparental care in the dung beetle Onthophagus taurus. Animal Behaviour, 64, 65-75.
Simmons, L.W. (2002). Confidence of paternity and parental care: covariation revealed through the experimental manipulation of the mating system in the beetle Onthophagus taurus. Journal of Evolutionary Biology, 15, 784-795.
Hunt J, Simmons LW (2002). The genetics of maternal care: direct and indirect genetic effects on phenotype in the dung beetle Onthophagus taurus.
Proc Natl Acad Sci U S A,
99(10), 6828-6832.
Abstract:
The genetics of maternal care: direct and indirect genetic effects on phenotype in the dung beetle Onthophagus taurus.
While theoretical models of the evolution of parental care are based on the assumption of underlying genetic variance, surprisingly few quantitative genetic studies of this life-history trait exist. Estimation of the degree of genetic variance in parental care is important because it can be a significant source of maternal effects, which, if genetically based, represent indirect genetic effects. A major prediction of indirect genetic effect theory is that traits without heritable variation can evolve because of the heritable environmental variation that indirect genetic effects provide. In the dung beetle, Onthophagus taurus, females provide care to offspring by provisioning a brood mass. The size of the brood mass has pronounced effects on offspring phenotype. Using a half-sib breeding design we show that the weight of the brood mass females produce exhibits significant levels of additive genetic variance due to sires. However, variance caused by dams is considerably larger, demonstrating that maternal effects are also important. Body size exhibited low additive genetic variance. However, body size exerts a strong maternal influence on the weight of brood masses produced, accounting for 22% of the nongenetic variance in offspring body size. Maternal body size also influenced the number of offspring produced but there was no genetic variance for this trait. Offspring body size and brood mass weight exhibited positive genetic and phenotypic correlations. We conclude that both indirect genetic effects, via maternal care, and nongenetic maternal effects, via female size, play important roles in the evolution of phenotype in this species.
Abstract.
Author URL.
Moczek AP, Hunt J, Emlen DJ, Simmons LW (2002). Threshold evolution in exotic populations of a polyphonic beetle. Evolutionary Ecology Research, 4, 587-601.
2001
Allen GR, Hunt J (2001). Larval competition, adult fitness, and reproductive strategies in the acoustically orienting ormiine Homotrixa alleni (Diptera : Tachinidae).
JOURNAL OF INSECT BEHAVIOR,
14(3), 283-297.
Author URL.
Hunt J, Simmons LW (2001). Status-dependent selection in the dimorphic beetle Onthophagus taurus.
Proceedings of the Royal Society B: Biological Sciences,
268(1484), 2409-2414.
Abstract:
Status-dependent selection in the dimorphic beetle Onthophagus taurus
The occurrence of alternative reproductive phenotypes is widespread in most animal taxa. The majority of known examples best fit the notion of alternative tactics within a conditional strategy where the fitness pay-offs depend on an individual's competitive ability or status. Individuals are proposed as 'choosing' the tactic that maximizes their fitness, given their status relative to ochers in the population. Theoretically, status-dependent selection should determine when an animal should switch between alternative tactics. While a number of studies have demonstrated unequal fitness pay-offs associated with alternative tactics, none, to our knowledge, have examined the fitness functions necessary for predicting when individuals should switch between tactics. Here, we use a dimorphic male beetle in order to provide the first empirically derived fitness function across alternative reproductive phenotypes. Our data provide empirical support for a game-theoretic conditional strategy that has evolved under status-dependent selection.
Abstract.
2000
Hunt J, Allen GR (2000). Larval density and developmental instability in the acoustically orienting parasitoid Homotrixa alleni.
Acta Ethologica,
2(2), 129-132.
Abstract:
Larval density and developmental instability in the acoustically orienting parasitoid Homotrixa alleni
The relationship between developmental stress caused by intraspecific larval density and fluctuating asymmetry (FA) was examined in the tachinid parasitoid Homotrixa alleni. Individuals reared in larger clutches were significantly smaller in body size when they emerged as adults. As predicted, smaller individuals were shown to have significantly higher levels of FA in their tibiae. This negative relationship was consistent across each pair of tibia and the magnitude of FA was also significantly correlated between tibiae. The exact nature of the observed relationship between larval density and FA in H. alleni remains speculative. © Springer-Verlag and ISPA 2000.
Abstract.
Hunt J, Simmons LW (2000). Maternal and paternal effects on offspring phenotype in the dung beetle Onthophagus taurus. Evolution, 54, 936-941.
1999
Hunt J, Kotiaho JS, Tomkins JL (1999). Dung pad residence time covaries with male morphology in the dung beetle Onthophagus taurus.
Ecological Entomology,
24(2), 174-180.
Abstract:
Dung pad residence time covaries with male morphology in the dung beetle Onthophagus taurus
1. The immigration and emigration behaviours of Onthophagus taurus were investigated in a combination of field and laboratory experiments to examine patterns of dispersal in this species. 2. On average, the mean proportion of major males immigrating to baited pitfall traps decreased significantly with time. In contrast, the mean proportion of minor males and females did not change with time. 3. The time taken to emigrate from a dung pad differed significantly among major males, minor males, and females. This difference arose because major males spent a significantly shorter period of time residing within the dung pad. On average, more than 50% of major males had emigrated from the dung pads after 30 h, some 4 h earlier than minor males and females. 4. When the effects of body size were controlled, major males with longer horns were shown to have longer wings. Because major males spend more time in flight, longer wings may be an adaptation to more frequent dispersal. Alternatively, longer wings in major males may compensate for the production of aerodynamically costly horns.
Abstract.
Simmons LW, Tomkins JL, Kotiaho JS, Hunt J (1999). Fluctuating paradigm.
Proceedings of the Royal Society B: Biological Sciences,
266(1419), 593-595.
Abstract:
Fluctuating paradigm
A prominent paradigm in evolutionary biology over the last ten years has been the role of fluctuating asymmetry in sexual selection. Fluctuating asymmetry in bilaterally paired traits, and in particular sexual traits, has been proposed to be a reliable indicator of individual quality and the focus of selection through sexual competition and attractiveness. We surveyed the literature on fluctuating asymmetry and sexual selection and found a marked chronological decline in the proportion of studies supporting the paradigm through the 1990s. Our data are supported by an independent meta-analysis of the literature. The data conform with the notion of a scientific revolution in which the early phase of a paradigm change is characterized by a publication bias, a less critical approach to research, or both. The patterns we observe in the fluctuating asymmetry literature suggest caution in drawing general conclusions from meta-analyses conducted before revolutions have settled.
Abstract.
Allen GR, Kamien D, Berry O, Byrne P, Hunt J (1999). Larviposition, host cues, and planidial behavior in the sound-locating parasitoid fly Homotrixa alleni (Diptera: Tachinidae).
Journal of Insect Behavior,
12(1), 67-79.
Abstract:
Larviposition, host cues, and planidial behavior in the sound-locating parasitoid fly Homotrixa alleni (Diptera: Tachinidae)
Some groups of tachinid flies deposit mobile first-instar larvae (or planidia) on or near their host. Flies within one such group, the tribe Ormiini, parasitize singing species of ensiferan Orthoptera and use sound for long distance host location. However, what induces tachinids to larviposit and whether planidia use any cues actively to locate their host remains poorly known. This paper examines the larviposition and planidial behavior of the ormiine Homotrixa alleni in relation to its bushcricket host, Sciarasaga quadrata. Sound alone was sufficient to elicit larviposition in gravid female H. alleni, where females arriving at an arena placed over a speaker broadcasting host song deposited an equal number of planidia in the presence or absence of a silent S. quadrata. Flies were observed to larviposit by forcibly expelling planidia up to 6 cm in a forward direction from the fly, with less than half of the trials with a host present resulting in physical contact between the host and the fly. In the host's absence, flies walked around the arena significantly more often, remained on the arena for the experimental duration (10 min), and changed orientation frequently. In the host's presence, flies generally maintained a position facing the host, stayed in the quadrant of first approach, and typically flew off the arena within 2 min of arrival. When the oncoming fly approached a forward facing host, more planidia were found in the arena's center (i.e. closer to the host) than in the no-host or rearward-facing host treatment. Planidia experimentally placed on a circular arena averaged 1 cm of movement in 15 min but none of the following cues-host song, host song with song-vibration transmission, a silent host, and a silent host with host movement-vibration transmission-significantly affected the direction or distance planidia traveled. At 20 ± 1°C, over half of the planidia died within 1 h and all died within 2 h of deposition. The significance of these results in relation to reproductive strategies and parasitism is discussed.
Abstract.
Simmons LW, Tomkins JL, Hunt J (1999). Sperm competition games played by dimorphic male beetles.
Proceedings of the Royal Society B: Biological Sciences,
266(1415), 145-150.
Abstract:
Sperm competition games played by dimorphic male beetles
Reproductive strategies often consist of two alternative tactics whereby males either compete for and guard females, or sneak copulations. By their nature, alternative tactics expose males to differing risks of sperm competition; sneaks will always be subject to sperm competition but guards will be subject to sperm competition with low probability, dependent on the number of sneaks. Recent game-theoretical models predict that males in the sneak role should have the greater gametic expenditure but that the disparity in expenditure should decrease with increasing numbers of sneaks. Male dung beetles in the genus Onthophagus can be separated into two morphs: major males have horns and guard females whereas minor males are hornless and sneak copulations. Here we compare testis size and ejaculate characteristics between these alternative morphs. We find that in O. binodis 30% of males are sneaks, and sneaks have larger testes, ejaculate volumes, and longer sperm than guards. In O. taurus 60% of males are sneaks and there are no differences in gametic traits. Our data thus provide empirical support for game-theoretical models of sperm competition.
Abstract.
1998
Hunt J, Allen GR (1998). Fluctuating asymmetry, call structure and the risk of attack from phonotactic parasitoids in the bushcricket Sciarasaga quadrata (Orthoptera: Tettigoniidae).
Oecologia,
116(3), 356-364.
Abstract:
Fluctuating asymmetry, call structure and the risk of attack from phonotactic parasitoids in the bushcricket Sciarasaga quadrata (Orthoptera: Tettigoniidae)
The acoustically orienting parasitoid Homotrixa alleni (Diptera: Tachinidae) is a significant mortality factor of calling male Sciarasaga quadrata (Orthoptera: Tettigoniidae), with less than 10% of males escaping parasitism within the duration of the calling season. This study examined fluctuating asymmetry (FA) (small, random deviations from perfect symmetry) in five morphological traits in S. quadrata and its relation to the survival of calling males in the field. A significant relationship was demonstrated in only a single trait; across three consecutive field seasons and among each of the collections per season, parasitised males were shown to have significantly more asymmetric hind tibia than unparasitised males. Since the morphological development of males is complete prior to parasitoid attack, this relationship is not caused by the activities of the parasitoid. Further experimentation revealed that there was no relationship between the level of FA in the hind tibia and the success of parasitism, with males artificially parasitised in the laboratory showing no difference in FA from those where parasitism was unsuccessful. Instead, FA was shown to be negatively related to chirp length, an aspect of call structure that significantly affects the survival of calling males under parasitism risk in the field. We explore the possible reasons why more asymmetric males produce calls of shorter chirp length and hypothesise that the difference in hind tibia asymmetry seen between parasitised and unparasitised males in the field is related to host location in H. alleni rather than the inability of S. quadrata to defend itself against parasitoid attack.
Abstract.
Hunt J, Simmons LW (1998). Patterns of fluctuating asymmetry in beetle horns: No evidence for reliable signaling.
Behavioral Ecology,
9(5), 465-470.
Abstract:
Patterns of fluctuating asymmetry in beetle horns: No evidence for reliable signaling
Negative relations between trait size and levels of fluctuating asymmetry in secondary sexual traits have been claimed to be indicative of honest signaling of male quality. Comparative studies of beetle horns have been used to illustrate the required negative relation between trait size and asymmetry. However, such studies may be confounded by measurement error or sampling bias clue to population differences or differences within species in the phenotypic expression of hornedness. We examined the patterns of fluctuating asymmetry within two species of horned beetle. We found that, in agreement with theory, horns exhibit greater asymmetry than naturally selected traits. However, we found a strong positive relation between horn size and asymmetry in Onthophagus taurus, a species with male dimorphisms, and a fiat relation in Bubas bison, a species with continuous variation in horn size. We suggest that these differences may reflect functional differences in horns. We conclude that patterns of asymmetry in horned beetles do not support the notion of honest signaling.
Abstract.
Hunt J, Simmons LW (1998). Patterns of parental provisioning covary with male morphology in a horned beetle (Onthophagus taurus) (Coleoptera: Scarabaeidae).
Behavioral Ecology and Sociobiology,
42(6), 447-451.
Abstract:
Patterns of parental provisioning covary with male morphology in a horned beetle (Onthophagus taurus) (Coleoptera: Scarabaeidae)
Male dung beetles, Onthophagus taurus, are dimorphic for a secondary sexual trait, head horns. Horned males participate in the production of brood masses while hornless male do not. Here we examine the reproductive performance of females mated with males exhibiting alternative horn morphologies. We found that exposure to males may be costly for females in that it reduced the total number of brood masses produced. However, females paired with horned males produced significantly larger brood masses than females paired with hornless males or females producing broods alone. We discuss the possible selection pressures that may underly horn evolution in this genus.
Abstract.
1997
Hunt J, Simmons LW (1997). Patterns of fluctuating asymmetry in beetle horns: an experimental examination of the honest signalling hypothesis.
Behavioral Ecology and Sociobiology,
41(2), 109-114.
Abstract:
Patterns of fluctuating asymmetry in beetle horns: an experimental examination of the honest signalling hypothesis
Recent theoretical arguments have claimed that negative relationships between the size and symmetry of secondary sexual traits are indicative of honest signalling of male quality. The patterns of fluctuating asymmetry in beetle horns have been proposed to support the honest signalling hypothesis. Here we examine three assumptions of the hypothesis, (1) that traits are costly to produce; (2) the levels of fluctuating asymmetry are indicative of stress imposed during development; and (3) that males with larger traits should have more symmetrical traits, using the horned beetle, Onthophagus taurus. Experimental manipulations of brood mass were used to manipulate horn size and asymmetry. The development of horns was found to be environmentally determined and costly in terms of delayed development and increased risk of pre-adult mortality. Decreasing resource availability increased relative horn asymmetry. However, horn height was positively related to absolute horn asymmetry. While the results do support the hypothesis that sexual selection on secondary sexual traits should increase levels of fluctuating asymmetry, they provide no support for the notion that the patterns of asymmetry honestly signal male quality. Horns are used in disputes between males and may be indicative of male parental investment. Thus, we conclude that while horn size may be an indication of male quality, the patterns of fluctuating asymmetry are not.
Abstract.
