Sexual selection and speciation: from gametes to ornaments

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More than 130 years ago, Charles Darwin suggested that some plant and animal features might help individuals to obtain mates, even though those traits were detrimental to survival. Such 'sexually selected' traits, he said, are thus very different from survival traits that resulted from natural selection. Even though this was a major scientific discovery, it was largely ignored for more than a century for both sociological and scientific reasons. The past 30 years, though, has seen a major resurgence of interest in sexual selection due to the development of both sophisticated theories that make a variety of interesting predictions and new experimental, molecular and observational techniques that allow us to thoroughly test those theories. My research focuses on both precopulatory (mate attraction) and postcopulatory (fertilization) characteristics of animals to test and develop theory that will help us to better explain the diversity of animals that have evolved as a result of sexual selection. Our current research addresses two general questions: (1) Why is there so much variation in colour within and among species of birds? and (2) Why does the size, structure and behaviour of sperm vary so much from species to species? Thus, we are trying to understand how bright plumage of different colours helps male (and less often female) birds obtain mates of high quality. Our work on bird coloration is leading to a better appreciation of the nature of colour vision and the mechanisms by which colours are produced and displayed in nature. Our studies of sperm evolution are also designed to help us understand more about the diversity of animal structure and behaviour but they have some additional aquacultural, agricultural and medical applications in helping us to understand how a male's condition influences his sperm quality and fertilization success. It is becoming increasingly clear that both pre- and postcopulatory processes are important to the origin, diversification and maintenance of species, so our work makes an important contribution to the study of the speciation process.