Sex Change and Population Dynamics in Arisaema (Araceae) II. An Examination on the Evolutionary Stability of Sex Changing Schedule of A. serratum (Thunb.) Schott

Abstract The evolutionary stability of the sex-changing habit of Arisaema serratum was examined. To evaluate reproductive success through male functioin properly, the mathematical formulation of Kakehashi and Harada (1987) was employed. Individuals were classified by both their size and sexual state, and the genetic contribution of individuals was estimated by calculating their reproductive value. It was shown that in the size classes where sex change actually occurs, the reproductive values of males and females are basically the same. This means that the genetic contribution of individuals in these size classes is the same whether they are male or female, and no selection pressure is working to change the male ratio in these classes. Thus, it is concluded that the size at which sex change occurs is evolutionarily stable. The adaptive significance of the size of first reproduction was also discussed.