Evolution of Coloration and Mate Preferences Along Environmental Gradients

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The only barriers to reproduction between some closely related species are female mate preferences. Factors that cause female mate preferences, or the characteristics of males they are based on, to evolve (i.e., change over generations) can lead to the formation of new species. Scientists are just beginning to understand the role of the environment in this process. In guppies, a small stream-dwelling fish native to Trinidad, females prefer males with larger and "brighter" orange spots. The orange spots contain two types of pigments, one of which males can synthesize (drosopterins) and the other of which they must obtain from their food (carotenoids). The main source of carotenoids for guppies is algae, which grow on rocks in the stream. Wider streams make larger gaps in the forest canopy, and consequently receive more sunlight and have larger standing crops of algae. This project will examine how variation among streams in forest canopy cover affects the evolution of male coloration and female mate preferences. The methods will include field experiments, laboratory breeding experiments, color measurements, and biochemical analyses.The broader goal is to develop a deeper understanding of how the environment affects the evolution of mate preferences and the traits they favor. This study will contribute to our knowledge of biological diversity.