Abstracts (first author)
Sex roles in a demographic context: population consequences of individual fitness variance in sequential hermaphroditesPDF
When studying sex roles, we often focus on which is the most competitive or choosy sex and who is performing more parental care. In sequentially hermaphroditic fish the division of reproductive tasks is as fair as it can get, since each individual (with few exceptions) reproduce initially as one sex and then change into the other sex, from female to male in protogyny (PG) or vice versa in protandry (PA). In either case, the second sex is the larger sex and potentially more prone to be removed by size-selective fishing. Does the direction of sex change influence the overall demography of a population? Sex change has been mainly investigated from adaptive/ecological points of view, focusing on individual variations in fitness between the male and female phase of the life cycle. Moving from the individual to the population level, the overall variance in individual reproductive success (Vk) should influence the demographic trajectory of the population. To our knowledge, no studies have compared protandrous and protogynous animal species in a population genetic context. Indeed, PG and PA can be expected to lead to very different demographic scenarios. PG occurs when there is high potential for polygamy and results in strong social structures dominated by one large male. Since large males can monopolize multiple females in harems and small females tend to choose the larger males, Vk should be greater in PG than in PA; this is expected to reduce the effective population size (Ne), a key parameter in conservation biology. This trend is reinforced by the greater skew in sex-ratio typically observed in PG. Here we show that molecular and life-history-based estimates of Ne in several pairs of protogynous and protandrous fish lend support to the prediction that protogynous populations may have – based on comparable trait distributions – generally smaller effective size than protandrous ones, leading to valuable insights for conservation and management of marine resources.