Male choice of mates and mating resourcesin the rose bitterling (Rhodeus ocellatus)

The traditional view of sexual selection acting wholly through male–male competition and female choice has been challenged in recent years. An increasing body of experimental work has demonstrated a role for male choosiness over mates, influenced by cues, such as female body size, that correlate with fecundity. In addition, in resource-based mating systems, male preference for resources required for reproduction is predicted to match those of females. Using the rose bitterling, Rhodeus ocellatus, a fish that uses living freshwater mussels for oviposition, we investigated male response to females that varied in size and to oviposition sites that varied in quality. Male courtship behavior directed at females, and aggression directed at rivals, did not vary with female size. The lack of predicted male response, which contrasts with other species, was explained by the absence of a relationship between female size and either batch fecundity or egg size, stemming from constraints on these variables imposed by oviposition in the gill cavities of mussels. When presented with spawning sites that contrasted in quality, male preferences for spawning sites were inconsistent: males lacked a preference for high-quality sites when no female was present but showed strong preferences for high-quality sites that matched the preferences of females. These results indicate constraints on the evolution of male mate choice and divergence in selection acting on the sexes in making oviposition decisions.