Male mating tactics and secondary sexual traits: insights from the Mediterranean killifish, Aphanius fasciatus

Context Sexual selection results from male competition and female choice linked by complex interactions that drive the population’s life history, often leading to the development of specific secondary sexual traits with an increased reproductive success. Aims To investigate the male mating tactics and the role of a secondary sexual trait (‘black band’ on the caudal fin) along the male ontogenetic development in the Mediterranean killifish, Aphanius fasciatus (Valenciennes, 1821). Methods Male–male competition was investigated through a combination of an extensive field collection and behavioural analysis under controlled conditions, comparing four groups differing in the presence or absence of the black band and body size. Key results Banded males courted more and tended to monopolise the female, but the overall spawning performance did not differ significantly among the analysed groups. Conclusion (1) The black band on the caudal fin depends on ontogeny; (2) all mature males express the entire courtship and competitive repertory; (3) sexual maturity occurs in fish of at least 20 mm; (4) large size and presence of the black band seem to contribute to male dominance. Implications This study has highlighted the role of Aphanius fasciatus as an excellent model for studying polygynandrous mating systems, on the basis of intense male–male competition.