One of the most enduring questions in sexual selection is why mate choice evolves for males with the most extravagant sexual ornaments and displays. One popular hypothesis posits that male sexual ornaments reveal male genetic quality, so that choosy females transmit "good genes" to offspring.
We are addressing key predictions of this “good genes” hypothesis using Drosophila bipectinata as our model.
Males of this species possess spectacular sex combs, a sexual ornament diverging genetically throughout the species’ range. This system, with it mosaic of differentiating populations throughout the South Pacific, offers a unique natural laboratory in which to study evolution by sexual selection in action!
We are studying the following:
Sex in nature: We are studying the direction and strength of pre-copulatory sexual selection on ornament size and asymmetry in field population in Australia, New Caledonia, Fiji and Taiwan.
Links to ejaculate quality: In recent experiments conducted at the University of Western Australia in collaboration with Leigh Simmons and Joe Tomkins, we have tested the hypothesis that ornament size reveals genetic differences among males in components of condition and ejaculate quality that mediate post-copulatory sexual selection.
Fluctuating asymmetry (FA): We have been testing hypothesis about the relative importance of trait FA and size on male mating success. Quantitative genetics experiments done in collaboration with Phil Taylor have tested key assumptions of the FA-sexual selection hypothesis, pertaining to the heritability of FA and its condition dependence relative to other traits of males.
Trait function: With a cutting-edge laser ablation system uniquely developed in our laboratory, we are able to perform high-precision surgery on live flies. By experimentally reducing comb size, integrated with behavioral, acoustic and genetic analyses, we are getting at the precise function of this ornament in courtship and in social signaling.
Female choice: Several ongoing experiments are testing whether sex comb size is subject to pre- and post-copulatory mate selection. Our laser ablation technique, coupled with ultra high-speed video, offer effective avenues into these questions.
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