性选择与性进化.ppt

性选择与性进化 Charles Darwin laid the foundation for all modern work on sexual selection in his seminal book The Descent of Man, and Selection in Relation to Sex. In this work, Darwin fleshed out the mechanism of sexual selection. He went well beyond a simple description of the phenomenon by providing extensive evidence and considering the far-reaching implications of the idea. Why does mate choice evolve at all? What factors determine the intensity of sexual selection in each sex? Darwin failed to appreciate that male–male competition and sexual selection can continue even after copulation has begun. The postcopulatory equivalents of both direct male–male battles (sperm competition) and female choice (cryptic female choice) occur within the female’s body. These include the hyper-diverse and paradoxically elaborate morphology of both sperm and male genitalia, the equally puzzling and elaborate morphology of nongenitalic male structures that are specialized to grasp and stimulate females, powerful manipulative effects of substances in male semen on female reproductive physiology, paradoxical male courtship behavior that occurs after copulation has already begun, variability in parental investments, and the puzzlingly complex and diverse interactions between sperm and female products that surround animal eggs and between male gametophytes and female tissues in flowering plants Geoff Parker, was a pioneer in ‘sperm competition’. When females mate with more than one male, Geoff noticed that the sperm would compete to fertilise the eggs. He wrote a groundbreaking paper in 1970. For a few years people thought the concept only applied to insects – Geoff’s speciality. In the following decade, there was an incredible realisation that female promiscuity was largely ubiquitous in the animal kingdom. Darwin had said exactly the opposite – that most females were strictly monogamous. Darwin assumed that the competition stopped once a partner was acquired. Geoff’s idea w