Protandry: the Relationship between Emergence Time and Male Fitness in the Pitcher-plant Mosquito

Protandry is the emergence or arrival into a seasonal population of males before females and is widespread among both plants and animals. Conceptually, protandry should be subject to stabilizing selection because early emerging males risk death before mating and late-emerging males miss opportunities to mate. However, for any given male, the optimal emergence time may depend upon the mean and distribution of emergence of other males in the population. Using lifetime offspring sired as our criterion of reproductive success, we found that, in laboratory populations of the pitcher-plant mosquito, Wyeomyia smithii, there is, indeed, stabilizing selection acting on the optimal time for male emergence, and that the specific optimum does depend upon emergence time of other males in the population. In addition, male cohorts achieved greater reproductive success when their emergence was spread over several days rather than occurring in a single day. However, reproductive success did not differ between normal and superdispersed emergence distributions, suggesting that, under more variable, natural conditions, the specific pattern of male emergence may be far less important than variation in emergence time, per se.