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. I have utilized a variety of empirical techniques including classical quantitative genetics, behavioral studies, genotyping using microsatellite markers, and field work to do so. Guppies respond strongly to the specific social context they are placed in (Bleakley et al. J. Evol. Bio. 2007). Using inbred lines I developed (Bleakley et al. Behav. Gen. 2006, Zebrafish 2008), I demonstrated that guppies significantly alter their behavior in response to the genetic composition of their social group, providing some of the first empirical measurements of the strength of such genetic interactions between individuals and generating a hypothesis for how reciprocal cooperation may evolve in unrelated individuals (Bleakley and Brodie Evol. 2009).