Evolution in the Context of the Environment.

Ecology can strongly influence evolution. To fully understand the evolutionary history of a species, it is essential to consider evolution within the context of the environment. Here, I explore how the environment produces different evolutionary patterns between populations and species, while considering how evolution in turn affects ecological patterns of distribution and population viability. Within a single population, the environment can affect whether polymorphisms are maintained or lost. Using a population genetic model, I show how natural and sexual selection can result in the maintenance of male color polymorphisms (MCPs) in a single population. Specifically, I find that microhabitat heterogeneity can lead to MCP maintenance despite asymmetries in the strengths of natural and sexual selection and in microhabitat proportions. Also, while sexual selection alone is often sufficient for polymorphism maintenance, natural selection alone results in polymorphisms under only unrealistic conditions. In comparing multiple populations, the environment influences population viability. When female mate choice is environmentally dependent, adaptive mate choice may affect the probability of population extinction. Here, I suggest how both the targets of mate choice and the fitness tradeoffs that females face influence extinction risk. I then describe how differential extinction risk in turn contributes to ecological patterns in species distribution and community composition and macroevolutionary processes including speciation and species level selection. Finally, I examined how the environment can influence range dynamics and species interactions in two spadefoot toad species. First, I used museum specimens to describe recent changes in species distribution. I found that these species have co-occurred in southern Arizona for at least 100 years. I also found that collection effort was more consistent in range interiors than at the periphery, making it difficult to interpret patterns of distribution at the range edge. Next, I used ecological niche modeling to determine how both abiotic and biotic factors contribute to species interactions. This work offers specific predictions that can be tested experimentally, while providing further evidence of the role of competition in driving species distributions. Together, these projects illustrate how both abiotic and biotic environmental factors dictate species distribution and abundance and thus potentially influence species interactions.