Dissertation Research: Conflict and the Evolution of Dimorphism in the Trinidadian Guppy

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Evolutionary biologists study the diversity of life on our planet and how it has been generated. One particularly important question is the diversity between sexes. While males and females are different in obvious ways related to reproduction, they also differ in other features. These additional differences are puzzling because the sexes share nearly all of their genes, and this suggests that different forms of some of those genes must be found in males and females. These differences should create a conflict between genes favored in females and genes favored in males. This research is looking for evidence of that conflict and, more importantly, whether that conflict is an unavoidable feature of having two sexes. The research will examine how males and females of the Trinidadian guppy evolve in response to a new environment. It will take advantage of an eight-year experimental study of evolution to ask if the conflict between sexes has been visible from the start or whether it emerges only after both sexes have adapted to the major features of a novel environment. Outreach to the public and K-12 students will occur as part of this project, and undergraduates from underrepresented groups will be involved in the research.  The strength and direction of natural selection on phenotypic variation is not equal among all individuals within a population. In particular, genetic correlations between the sexes can produce intralocus sexual conflicts when selection acts antagonistically between males and females.  Recent work has shed light on the evolutionary constraint that sexually antagonistic selection can produce, but its role in the general process of adaptation remains unclear. Theory suggests that intralocus sexual conflict will be minimal in a population adapting to a novel environment and will emerge only when populations approach their adaptive peaks. This research will address the role of intralocus sexual conflict on the adaptive process by answering these questions: (1) Does sexually antagonistic selection and the resulting sexual conflict influence the adaptive process from the start or does it have more of an influence later when trait values approach their optimum? (2) Does the antagonistic relationship between the sexes change over time allowing for or limiting the evolution of sexual dimorphism? This project integrates the experimental study of evolution with the statistical tools of a large-scale mark-recapture project and next-generation sequencing. Genetic and phenotypic samples are available for nearly every guppy within these experimental populations dating to the start of the experiment. These data provide the opportunity to estimate fitness, mate choice, trait heritability, and the genetic covariance between the sexes. Using this system and these methods, the researchers will answer questions on the genetics of adaptation in a manner not previously possible.