Post-copulatory intra- and intersexual selection at fertilization in a polygamous fish

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In the past decades, studies on sexual selection have increased exponentially and are a major research theme in Evolutionary Biology. Work on pre-copulatory sexual selection (usually male-male competition and female mate choice) and post-copulatory sexual selection (sperm competition and cryptic female choice like non-random fertilization) have developed independently for a long time. In recent years, one can see a clear trend in integrating the two levels of sexual selection. There are, however, still several ambiguous topics in post-copulatory sexual selection like functional variation in sperm design. Moreover, there are few model systems in which both levels of sexual selection are studied in detail. Finally, there is a gap in our knowledge about the evolvability of sperm traits. Data on genetic variation and covariation are lacking altogether in fish. In our proposal we want to promote the study of post-copulatory sexual selection in three-spined sticklebacks, Gasterosteus aculeatus, which is well-studied with respect to pre-copulatory sexual selection. Sneaking, and thus sperm competition is common in this fish species with external fertilization. In recent years we have advocated sticklebacks as very promising subjects for post-copulatory sexual selection. We plan to test the prerequisites for phenotypic evolution of sperm, that is, the estimation of genetic variation and covariation of sperm and testes traits and male breeding coloration as well as specific environmental effects like the influence of food ration, carotenoids, ultraviolet radiation, and specific parasites on sperm traits and associated function. The second aim concerns intra- and intersexual selection at the level of fertilization. In vitro sperm competition will be studied with respect to delayed ejaculation in sneakers and environmentally induced changes in sperm design, whereas cryptic female choice at fertilization will be studied in vitro with respect to kin. Additionally, ejaculate characteristics will be studied in relation to female attractiveness, female relatedness, and sperm aging. The third aim will look at long-term consequences of sperm competition by comparing sperm and testes among the different species of the stickleback family, the Gasterosteidae, and among various populations of the three-spined stickleback.