Relationships between relative size of sexual traits and male mating success in the Mediterranean killifish Aphanius fasciatus (Nardo, 1827)

Some relationships between the relative size of secondary sexual traits and male mating success were investigated in the killifish Aphanius fasciatus (Nardo, 1827). The relative ability of a male to compete with another male for access to a ripe female was related to the relative size of male sexual traits by means of a behavioural experiment under controlled laboratory conditions. Furthermore, the covariation in the expression of sexual traits was analysed from a sample of field-collected males. Results of the behavioural experiment showed that male dominance and success were positively related to the relative height of the dorsal fin, but not to the pattern of vertical bars along body sides. Within the analysed male population, males with larger fins tended to have thinner bars, whereas there was no statistically significant correlation with bar number or with bar asymmetry. The results were discussed in terms of advantages conferred by larger dorsal fins in killifish breeding systems, and developmental constraints defining a multiple set of traits correlated to male quality were also hypothesised. © 2010 Taylor & Francis.