Discrete and continuous reproductive tactics in a hermaphroditic society
An important step towards understanding conflicts in animal societies lies in identifying socioecological predictors of individual reproductive tactics. In gonochoristic species, individuals can choose to adopt breeding or nonbreeding tactics, and if they breed, how large a share of reproduction they acquire. In hermaphroditic species, individuals can also adopt male or female breeding tactics. Hermaphrodites' wider suite of reproductive options makes them interesting models for investigating predictors of reproductive tactics. We used molecular and ecological data to determine socioecological correlates of discrete (breeding versus nonbreeding; males versus female) and continuous (share of reproduction) reproductive tactics in the hermaphroditic coral-dwelling fish, Dascyllus aruanus. The number of potential competitors within groups was positively related to coral size, and the amount of total reproduction over which they competed was associated with the size of the largest individual (i.e. the parental male). Discrete and continuous reproductive tactics were strongly influenced by rank and body size: high-ranking and large individuals were more likely to breed and attain larger reproductive shares and output. High-ranking breeders also obtained a larger reproductive output if they adopted male tactics, whereas low-ranking breeders obtained a larger share if they adopted female tactics, which can explain why these fish show protogynous sex change. Genetic analysis also revealed that subordinates could attain a larger reproductive share than dominants, and that extragroup individuals could contribute to reproduction. Our results shed new light on the causes of variation in reproductive tactics, the payoffs from group membership and the nature conflict in hermaphroditic societies.
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