The interplay between natural and sexual selection: causes and consequences

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My students and I study the evolution of and flexibility in animal reproductive strategies. Here, we focus on Trinidadian guppies, a small freshwater fish, that shows considerable variation in male sexual traits and in female mate choice preferences. Our previous work suggests that females' main mate preference, for orange spots on males, originated with a foraging bias for orange-coloured fruit. We are testing several explanations for the inter-population variation in this bias for orange. For example, does it result from differences in colour vision, which might have evolved in response to differences in their habitats, including a predator that uses orange spots on its claws to lure guppies? Female guppies also use a second criterion for selecting mates-they prefer males with rare or novel colour patterns. This may help them to avoid mating with relatives and thus reduce the risk of serious genetic disorders in their offspring; this 'rare male' effect can also contribute to the maintenance of high levels of genetic diversity. Here, we will determine if males with common, and thus distasteful, colour patterns engage in risky behaviours attempting to find mates. Another goal is to determine the neurological basis for this mate preference. Has it evolved as part of a suite of responses to novelty, including a motivation to explore new, potentially productive habitats or sources of food? We are focusing on the role of dopamine because it influences responsiveness to novelty in a wide range of animals, including humans. Some of the most productive areas of research are at the interface between studies of natural behaviour variants and neurobiology. Few studies have documented variation in mate choice preferences across multiple populations and, with our rich understanding of guppy ecology and evolution, this is a rare opportunity to fully understand the factors responsible for this variation. Biologists managing and conserving Canadian wildlife will benefit from our findings; for example, our insights (i) may enhance captive breeding programs where animals have been reluctant to mate and (ii) should improve our understanding of local adaptation so that the costs and benefits of within- versus between population crosses can be evaluated.