Andrea Pilastro Biology Department of the University of Padova, Italy Title Post–copulatory sexual selection in the guppy Abstract Sexual selection is the evolutionary process that favours those traits that confer a reproductive advantage. In the classical Darwin’s view, this process was exclusively precopulatory because he assumed females to be sexually monogamous. However, it has recently become clear that often females actively seek copulation with multiple partners. This implies that sexual selection continues after copulation up to the point of fertilization. Postcopulatory sexual selection comprises both male–male competition, in the form of sperm competition (the competition between the sperm of different males to fertilize the same batch of eggs), and cryptic female choice (a female’s ability to bias the fertilization success of the males that copulate with and inseminate her). Postcopulatory sexual selection has proven to be a pervasive evolutionary force influencing a variety of morphological, behavioural and physiological reproductive traits in both males and females. In a few cases, it has been demonstrated that postcopulatory sexual selection can reinforce the evolution of the same traits that are favoured by the precopulatory sexual selection. One of these cases is the guppy, a small freshwater fish with internal fertilisation and intense sperm competition, in which females prefer to mate with more colourful males. I will present the results of a series of experiments showing that more attractive males are favoured in postcopulatory selection because they produce more competitive ejaculates and females allow them to transfer more sperm during copulation. Preliminary results suggest that some sperm traits have a sire heritability, suggesting indirect genetic benefits for promiscuous females. CV I am at the Biology Department of the University of Padova since 1998 (senior researcher, 1998–2004, associate professor, 2005–). My research interests focus on sexual selection and sexual conflict in fishes and birds. In particular, I am interested in the mechanisms of post–copulatory sexual selection and the relationship between secondary sexual characters and sperm competition in poeciliids, mainly in the guppy (Poecilia reticulata). I am also doing some work on mutual sexual selection, sexual conflict and extra–pair paternity in birds.   Selected recent publications Scaggiante M, Rasotto MB, Romualdi C, and Pilastro A. 2005. Territorial male gobies respond aggressively to sneakers but do not adjust their sperm expenditure. Behav Ecol (doi:10.1093/beheco/ari081) Griggio M, Valera F, Casas A, and Pilastro A. 2005. Males prefer ornamented females: a field experiment of male choice in the rock sparrow. Anim Behav 69:1243-1250 Griggio M, Matessi G, and Pilastro A. 2005. Should I stay or should I go? Female brood desertion and male counterstrategy in rock sparrows. Behav Ecol 16:435-441 Evans JP, Kelley JL, Bisazza A, Finazzo E, and Pilastro A. 2004. Sire attractiveness influences offspring performance in guppies. Proc R Soc Lond B Biol Sci 271:2035-2042 Pilastro A, Simionato M, Bisazza A, and Evans JP. 2004. Cryptic female preference for colorful males in guppies. Evolution 58:665-669 Evans JP, Zane L, Francescato S, and Pilastro A. 2003. Directional postcopulatory sexual selection revealed by artificial insemination. Nature 421:360-363 Evans JP, Pierotti M, and Pilastro A. 2003. Male mating behavior and ejaculate expenditure under sperm competition risk in the eastern mosquitofish. Behav Ecol 14:268-273 Evans JP, Pilastro A, and Ramnarine IW. 2003. Sperm transfer through forced matings and its evolutionary implications in natural guppy ( Poecilia reticulata) populations. Biol J Linn Soc 78:605-612 Griggio M, Matessi G, and Pilastro A. 2003. Male rock sparrow (Petronia petronia) nest defence correlates with female ornament size. Ethology 109:659-669 Pilastro A, Benetton S, and Bisazza A. 2003. Female aggregation and male competition reduce costs of sexual harassment in the mosquitofish Gambusia holbrooki. Anim Behav 65:1161-1167 Pilastro A, Griggio M, and Matessi G. 2003. Male rock sparrows adjust their breeding strategy according to female ornamentation: parental or mating investment? Anim Behav 66:265-271 Pilastro A, Tavecchia G, and Marin G. 2003. Long living and reproduction skipping in the fat dormouse. Ecology 84:1784-1792 Evans JP, Kelley JL, Ramnarine IW, and Pilastro A. 2002. Female behaviour mediates male courtship under predation risk in the guppy (Poecilia reticulata). Behav Ecol Sociobiol 52:496-502 Matessi G, Griggio M, and Pilastro A. 2002. The geographical distribution of populations of the large-billed subspecies of reed bunting matches that of its main winter food. Biol J Linn Soc 75:21-26 Pilastro A, Scaggiante M, and Rasotto MB. 2002. Individual adjustment of sperm expenditure accords with sperm competition theory. Proc Natl Acad Sci USA 99:9913-9915 Pilastro A, Griggio M, Biddau L, and Mingozzi T. 2002. Extrapair paternity as a cost of polygyny in the rock sparrow: behavioural and genetic evidence of the 'trade-off' hypothesis. Anim Behav 63:967-974 Pilastro A, Evans JP, Sartorelli S, and Bisazza A. 2002. Male phenotype predicts insemination success in guppies. Proc R Soc Lond B 269:1325-1330 Saino N, Ambrosini R, Martinelli R, Calza S, Møller AP, and Pilastro A. 2002. Offspring sexual dimorphism and sex-allocation in relation to parental age and paternal ornamentation in the barn swallow. Mol Ecol 11:1533-1544 Bisazza A, Vaccari G, and Pilastro A. 2001. Female mate choice in a mating system dominated by male sexual coercion. Behav Ecol 12:59-64 Pilastro A, Biddau L, Marin G, and Mingozzi T. 2001. Female brood desertion increases with the number of available mates in the Rock Sparrow. J Avian Biol 32:68-72 Pilastro A, Pezzo F, Olmastroni S, Callegarin C, Corsolini S, and Focardi S. 2001. Extrapair paternity in the Adelie Penguin Pygoscelis adeliae. Ibis 143:681-684 Bisazza A and Pilastro A. 2000. Variation of female preference for male coloration in the eastern mosquitofish Gambusia holbrooki. Behav Genet 30:207-212 Pilastro A and Bisazza A. 1999. Insemination efficiency of two alternative male mating tactics in the guppy (Poecilia reticulata). Proc R Soc Lond B 266:1887-1891 Pilastro A, Giacomello E, and Bisazza A. 1997. Sexual selection for small size in male mosquitofish (Gambusia holbrooki). Proc R Soc Lond B 264:1125-1129 Berglund A, Bisazza A, and Pilastro A. 1996. Armaments and ornaments: An evolutionary explanation of traits of dual utility. Biol J Linn Soc 58:385-399   Andrea Pilastro Department of Biology University of Padova Via U. Bassi 58/B I-35131 Padova, ITALY andrea.pilastro@unipd.it Home page: www.bio.unipd.it/behavecol/