Evolution and Mechanisms of Plasticity in Wild Baboons (Papio cynocephalus)

Abstract

In many species, early life experiences have striking effects on health, reproduction, and survival in adulthood. Thus, early life conditions shape a range of evolutionarily relevant traits, and in doing so alter the genotype-phenotype relationship and the phenotypic distribution on which selection acts. Because of the key role early life effects play in generating variation in fitness-related traits, understanding their evolution and mechanistic basis is crucial. To gain traction on these topics, my dissertation draws on ecological, demographic, and genomic data from a long-term study population of wild baboons in Amboseli, Kenya to address three major themes: (i) the adaptive significance of early life effects, (ii) the molecular mechanisms that connect early life experiences with later life traits, and (iii) the development of laboratory tools for understanding the role of one particular mechanism—DNA methylation—in translating environmental inputs into phenotypic variation. In chapter one, I empirically test two competing explanations for how early life effects evolve, providing novel insight into the evolution of developmental plasticity in long-lived species. In chapter two, I address the degree to which ecological effects on fitness-related traits are potentially mediated by changes in DNA methylation. Finally, in chapter three, I develop a high-throughput assay to improve our knowledge of the phenotypic relevance of changes in the epigenome. Together, this work provides some of the first empirical data on the genes and mechanisms involved in sensing and responding to environmental variation in wild mammals, and more generally addresses several critical gaps in our understanding of how early experiences affect evolutionarily relevant traits.