coevolution of male and female genital morphology in waterfowl男性和女性生殖器形态的共同进化的水禽.pdf

Coevolution of Male and Female Genital Morphology in Waterfowl 1,2 1 3 4 3 2 Patricia L. R. Brennan *, Richard O. Prum , Kevin G. McCracken , Michael D. Sorenson , Robert E. Wilson , Tim R. Birkhead 1 Department of Ecology and Evolutionary Biology, and Peabody Natural History Museum, Yale University, New Haven, Connecticut, United States of America, 2 Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, United Kingdom, 3 Institute of Arctic Biology, Department of Biology and Wildlife, and University of Alaska Museum, University of Alaska Fairbanks, Fairbanks, Alaska, United States of America, 4 Department of Biology, Boston University, Boston, Massachusetts, United States of America Most birds have simple genitalia; males lack external genitalia and females have simple vaginas. However, male waterfowl have a phallus whose length (1.5–.40 cm) and morphological elaborations vary among species and are positively correlated with the frequency of forced extra-pair copulations among waterfowl species. Here we report morphological complexity in female genital morphology in waterfowl and describe variation vaginal morphology that is unprecedented in birds. This variation comprises two anatomical novelties: (i) dead end sacs, and (ii) clockwise coils. These vaginal structures appear to function to exclude the intromission of the counter-clockwise spiralling male phallus without female cooperation. A phylogenetically controlled comparative analysis of 16 waterfowl species shows that the degree of vaginal elaboration is positively correlated with phallus length, demonstrating that female morphological complexity has co-evolved with male phallus length. Intersexual selection is