HERITABILITY OF DEVELOPMENT TIME AND PROTANDRY IN THE PITCHER-PLANT MOSQUITO, WYEOMYIA-SMITHII

Models of protandry (1) assume implicitly or explicitly that independe nt evolution of male and female preadult development times is possible and (2) assume or assert that protandry should increase in population s that are univoltine or at least composed of discrete, nonoverlapping generations. Herein we examine these assumptions in the pitcher-plant mosquito, Wyeomyia smithii. Heritability and additive generic varianc e of development time are higher in female than in male W. smithii. Pr otandry is higher in lines selected for slow development than in lines selected for fast development or in unselected control lines. Protand ry is therefore capable of evolving. Contrary to predictions based on sexual selection, southern populations with multiple, overlapping gene rations are just as protandrous as northern bi- and univoltine populat ions with discrete generations. Voltinism and developmental synchrony of the population do not appear to have been major selective factors i n the evolution of protandry in W. smithii. We propose that protandry can be maintained by natural selection in multivoltine populations wit h overlapping generations as a consequence of sexually dimorphic fitne ss criteria. Selection should minimize development time in males but m aximize growth rate in females. In W. smithii, females achieve higher growth rate than males but also harbor greater genetic variation for d evelopment time, indicating that selection has, indeed, minimized deve lopment time to a greater extent in males than in females. We conclude that if both natural and sexual selection are involved in the mainten ance of protandry in populations of W. smithii, then their relative im portance changes with the degree of generation overlap.