Empirical studies and theoretical discussion in the field of sexual selection suggest that male-male competition and female choice have postcopulation equivalents in polyandrous systems. Postcopulatory processes may affect sexual selection by increasing heterogeneity of fertilisation success of males. Sperm competition, the postcopulatory equivalent of male-male competition, has broad empirical and theoretical support. Postcopulatory female choice however, has proven difficult to demonstrate and is still the subject of controversies. One form of postcopulatory female choice, where females can discriminate between and differentially utilise the sperm of different males, is called sperm choice. One way to assess if sperm choice is occurring is to investigate the mechanism by which a female differentially use sperm from various males. A few studies have reached that goal by demonstrating that female chose the sperm of unrelated male over the sperm of relatives. Unambiguous tests of whether sperm choice is or is not occurring, are needed to test the generality of this process, and therefore its importance in evolution. This proposal aims to use molecular genetic techniques to determine patterns in sperm storage and paternity of wild-caught squid, to assess whether females have the potential for sperm choice. Loliginid squid have unique advantages related to novel aspects to their biology that will permit to acquire empirical data which support or refute this hypothesis. The project will determine:1. The incidence and pattern of multiple paternity within broods;2. If switches in paternity of embryos occurring along the length of egg strings is a consistent phenomenon in the wild.3. If the relationship between paternity and spermatophores located within particular deposition sites indicates female sperm choice, sperm competition or random fertilisation.4. If level of genetic similarity between a consort male and a female affect fertilisation success of the male.
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