Life History Evolution of Marine Gastropods with Determinate Growth.
2008/1/28 16:00~ (at The 3rd meeting room of the Biology Department)
Body size greatly affects the fitness of an individual through fecundity and survival, and thus the spatial variation is of a particular interest in evolutionary ecology. From life-history evolution point of views, I’m investigating the geographic variations of adult body size and the associated traits in intertidal gastropods with determinate growth, or cowries (Mollusca, Gastrpoda, Cypraeidae). The life history of cowries consists of three stages: shell volume increases in the juvenile stage, which is followed by the callus-building stage in which shell thickness increases, and then reproduction starts without further growth in the adult stage. In the first half of this presentation, I will talk on the theoretical study, in which the optimal growth schedule of cowries was calculated to specify the ultimate factors of the positive latitudinal cline of adult body size and negative latitudinal cline of callus thickness in Monetaria caputserpentis. In the second half, I will introduce the ongoing empirical studies aiming to elucidate the proximate factors of the equilatitudinal size variation among populations in Monetaria annulus. |
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