Meeting Abstract

S10-2.4  Saturday, Jan. 7  Life history and sexuality patterns in barnacles: A theoretical perspective YAMAGUCHI, S.*; SAWADA, K.; YUSA, Y.; Kyushu Univ., Fukuoka, Japan, JSPS; Grad. Univ. Adv. Stud. (SOKENDAI), Kanagawa, Japan; Nara Women’s Univ., Japan

Darwin (1851) found that barnacles have three sexuality patterns: hermaphroditism, androdioecy (coexistence of hermaphrodites and males) and dioecy (females and males). Males are always very small and associated with larger females or hermaphrodites, and are called "dwarf males". In this presentation, we review our theoretical studies on the evolution of sexuality patterns and male dwarfing in barnacles. The extent of male dwarfing (male body size relative to size of females or hermaphrodites) varies among barnacle species. In the first model (Yamaguchi et al. 2007), we studied optimal life history strategy to explain the variation in male body size. We concluded that poor food availability and reduced sperm competition due to dioecy (as compared with androdioecy) lead to extensive degree of male dwarfing. We (Yamaguchi et al. 2008) then expanded Charnov’s (1987) model on the evolution of barnacle sexuality to incorporate the settlement pattern of larvae and food availability. In our model, the three patterns of sexuality evolve depending on these parameters. In these models, size distribution is given in advance. However, size distribution, as well as sexuality patterns, is a result of life history evolution. Therefore, our next model (Yamaguchi et al. in prep.) integrated both life history theory and sex allocation theory. We investigated the effects of mortality and food availability on sexuality. Our model showed that rich food and low mortality lead to hermaphroditism, poor food and high mortality to dioecy, and intermediate conditions to androdioecy. We compare our results with information on various barnacle species, and aim to unify theoretical and empirical evidence.