Maintenance of Variation in Sexually Selected Traits: a Nutritional Ecology Approach

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How genetic variation is maintained in traits that enhance fitness remains a fundamental dilemma in evolutionary biology. Several major theories have been put forth to explain the persistence of genetic variance including genic capture, frequency dependent fitness, fluctuating selection, genotype-by-environment interactions, genotype-by-genotype interactions, heterosis, and antagonistic pleiotropy. My students and I are testing some of these theories using an animal behaviour approach that incorporates tools from nutritional ecology, ecological physiology, and quantitative genetics. Our laboratory-based empirical research quantifies the phenotypic and genetically based variation in condition, life-history traits, and sexually selected traits and determines how this variation is influenced by diet and physiology. Our first three research goals lay the foundation needed to test hypotheses for maintaining variation in fitness traits. We will estimate the structure of sexual traits and female preference functions to understand how traits are likely to experience selection; quantify how diet affects sexual traits to determine their condition-dependent nature; and assess how diet influences the physiological foundations of sexual trait variation. We will then test the genic capture hypothesis and quantify whether females receive indirect benefits from mating with preferred mates. Lastly, we will test whether frequency-dependent fitness can maintain variance in these sexual traits. Together this work will determine the multivariate structure of the sexual traits, their condition-dependent nature, their physiological and genetic underpinnings, whether females receive indirect benefits, and the potential for frequency-dependent fitness. Overall, our research will explicitly test two of the above theories for the maintenance of high genetic variance - genic capture and frequency-dependent fitness. Long-term, the overarching goal of my research program is to contribute to a more complete understanding of how high genetic variance is maintained in traits that enhance fitness.