UBC Theses and Dissertations
Local adaptation and maintenance of variation in heterogeneous environments Yeaman, Samuel
Most species inhabit environments that are spatially heterogeneous at some scale. If dispersal is low enough relative to spatial variations in the effect of natural selection, then local adaptations may emerge. On the other hand, if dispersal is high enough to prevent isolation by distance, then gene flow among populations will influence both the amount of standing genetic variation maintained within populations and the architecture of this variation. Here, I explore various genetic consequences of evolution in heterogeneous environments. I begin by reviewing two empirical studies exploring how heterogeneous selection and gene flow affect the maintenance of variation within populations. The first of these is an observational study of patterns in natural populations of Pinus contorta (lodgepole pine; Chapter 2), while the second is a manipulative laboratory evolution experiment using Drosophila melanogaster (Chapter 3). I then discuss three theoretical studies on the evolution of locally adaptive trait divergence between populations under migration-selection balance. The first of these develops analytical approximations to predict the invasion probability and persistence time of beneficial mutations in finite populations (Chapter 4). The second of these studies explores the effect of migration-selection balance on the evolution of the genetic architecture underlying a quantitative trait (Chapter 5). The final theoretical study presents an exploration of the discrepancies between quantitative genetic models of mutation-selection balance and observations based on individual-based simulations (Chapter 6). Taken together, this research contributes to our understanding of how gene flow and heterogeneous selection influence the genetics of adaptation and the maintenance of genetic variation.
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