Ecology & Evolution of Sexual Selection

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Sexual selection is a powerful agent of evolutionary change, as non-random mating increases individual variation in reproductive success, thereby altering the frequencies of alleles passed on from one generation to the next. While sexual selection is commonly associated with the evolution of elaborate morphological, behavioural and physiological traits in males, as well as preferences for some of these traits in females, there is a great deal that we still do not understand about its operation, and its short-and long-term impact on species adaptation & evolution. The current proposal integrates behavioural, ecological, evolutionary & genetic techniques to test hypotheses in 2 (not-mutually exclusive) areas of research: (1) the continued & expanded study of the causes & consequences of variation in female mate preferences; (2) tests of whether sexual selection is complementary or antagonistic to natural selection. Our research will use 2 species of fruit flies: D. melanogaster, which has served extensively as a model for courtship/mating behaviour & in which a number of powerful genetic tools are available; and the spotted-wing fly, D. suzukii, an invasive (& economically destructive) species. Area 1: While models of sexual selection assume, either implicitly or explicitly, that females all exhibit the same preferences for male traits, in reality, females often differ in their attraction towards prospective males. Inter-individual variation for mates alters the strength &/or direction of sexual selection, thereby altering a species’ evolutionary trajectory. Despite its potential importance, variation in female mate choice has been largely overlooked. Over the next 5yrs we shall continue exploring the genetic & environmental factors contributing to this variation, & the impact of variation to lifetime reproductive success in both males & females. We shall test whether individual preference variation is due to the multitude of different (& possibly conflicting) signals presented by prospective mates. Using experimental evolution, we shall measure how female preferences evolve in response to manipulated costs/benefits of mating. Area 2: The question whether, sexual selection promotes or impedes adaptive evolution is contentious. If traits favoured by sexual selection are signals of overall “quality”, then non-random mating will complement natural selection. However, if traits that increase individual reproductive success come at a cost of survival (or to members of the opposite sex), then natural & sexual selection will act in opposition, thereby interfering with the ability of species to adapt to their environment. We plan to test this empirically testing this using experimental evolution using Drosophila sp. as the opportunity (& intensity) of sexual selection, as well as the environment, can be easily manipulated, & meaningful measurements of individual fitness can be made.