Dr Bronwyn Bleakley
NSF Research Fellow
Daphne du Maurier
Daphne du Maurier Building, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK
2007 PhD in Biology (Area Certificate in Animal Behavior) from Indiana University
1997 BS in Ecology and Evolutionary Biology from University of Arizona
2007-2009 National Science Foundation International Research Fellow
I am fascinated by interacting phenotypes – traits that depend at least in part on an interaction between individuals. The evolution of interacting phenotypes is especially intriguing because the direction, magnitude and rate of behavioral evolution; the balance between natural, sexual and social selection; and the genetic architecture underlying interacting phenotypes are predicted to differ from non-interacting traits. My research currently utilizes two systems to explore how interacting phenotypes may evolve: guppy antipredator behavior and cannibalism in isopods.
Indirect Genetic Effects on Antipredator Behavior
Indirect genetic effects (IGEs), the impacts on an individual’s phenotype by genes carried in its social partners, provide a powerful framework for understanding how interacting traits may be generated and evolve. While selection acts on individuals, if IGEs impact an individual’s phenotype, how the individual experiences selection is also a function of genes carried in social partners. Predicting the outcome of selection operating on interacting phenotypes therefore requires information about the composition of the social group in which an individual is behaving. My work to date has focused on quantifying where the relevant genetic variation underlying guppy antipredator and social behavior resides: in the individual or its social group. Guppies respond strongly to the specific social context they are placed in (Bleakley et al. J. Evol. Bio. 2007) and significantly alter their behavior in response to the genetic composition of their social group. Working with Dr. Butch Brodie, using inbred lines I developed (Bleakley et al. Beh. Gen. 2006; Bleakley et al. Zebrafish in press) I am generating some of the first empirical measurements of the strength of such genetic interactions between individuals.
Guppy Strains Evolution of Interacting Phenotypes in Natural Populations
I am working to expand my laboratory studies to address how indirect genetic effects are likely to impact behavioral evolution in the wild. Wild guppy populations, which vary in many behavioral and life history characteristics due to differences in predation pressure, provide the ideal ecological context for understanding how interactions among individuals may impact the evolution of social behavior. For example, IGEs are predicted to generate extremely rapid evolution in systems that would otherwise evolve more slowly. Both behavior and life history characteristics of guppies are known to evolve very rapidly in response to predation pressure, perhaps in part because of IGEs within the system. The next phase of my research with guppies will explore the fitness consequences for individuals experiencing IGEs and how IGEs impact the magnitude and rate of behavioral evolution in this system.
Impact of Indirect Genetic Effects on the Evolution of Cannibalism
Cannibalism is most accurately described as an interacting phenotype, where both the initiation and outcome of a cannibalistic interaction are likely to be influenced by the phenotypes of both individuals in the interaction. Although the evolution of cannibalism has been well studied in some contexts, it has never been considered in the framework provided by interacting phenotype theory. I was awarded an NSF International Research fellowship to investigate the impacts of IGEs on the evolution of cannibalistic behavior both theoretically and experimentally. In collaboration with Professor Allen Moore and Dr John Hunt (University of Exeter, Centre for Ecology and Conservation), I am generating a set of explicit models describing the impacts of IGEs on the evolution of cannibalistic behavior. Second, in collaboration with Dr. Stephen Shuster (Northern Arizona University), I will test several critical predictions of the above models. Socorro isopods, Thermosphaeroma thermophilum, cannibalize smaller individuals in both sexes and at all developmental stages, even in the presence of alternative food sources, with the greatest risk for all individuals resulting from interactions with large males. Individuals are likely to experience dramatically different risks of cannibalization and significantly different probabilities of successfully cannibalizing others based on the individuals with which they are interacting. Body size in these isopods is heritable and has previously been demonstrated to evolve with the degree of cannibalism exhibited by a population. We will experimentally examine the influence of the social environment and IGEs on the rate of evolution of cannibalistic behavior body size.
Balance and interaction between modes of selection
Natural and sexual selection have long been recognized as important evolutionary forces. In contrast, social selection arising from interactions between conspecifics is an important selective force that remains largely unexplored. The relative effects of social, natural and sexual selection have only rarely been partitioned for natural populations and the impacts of IGEs on social selection have yet to be explored empirically. Systems with cannibalism provide a unique opportunity to partition the effects of social selection from natural and sexual selection acting concurrently in natural populations. The expression of cannibalism reflects an interaction between the relative body sizes of interactants, where the successful cannibalism results only when one interactant is larger. Cannibalism is therefore an interacting phenotype and generates social selection for increased body size. Sexual selection also impacts the evolution of body size in cannbalistic systems through fitness increases associated with mate guarding or clutch size. An additional component of my current collaboration with Drs. Shuster, Moore and Hunt however seeks to experimentally partition the influences of social and sexual selection on the evolution of body size and cannibalism in isopods.