INTRASPECIFIC LIFE-HISTORY VARIATION IN RADIX PLICATULUS (GASTROPODA,PULMONATA, LYMNAEIDAE)

Life-histories of Radix plicatulus (Benson, 1842) populations inhabiti ng two neighbouring sites on a Hong Kong stream were investigated. In one of the two sites, R. plicatulus co-occurred with high densities of Pomacea levior which is known to prey on the egg capsules and hatchli ngs of sympatric gastropods. On the basis of general life-history theo ry, I hypothesized that R. plicatulus which co-occurred with P. levier should exhibit a life-history strategy characterized by a delayed rep roduction, a longer recruitment period and a larger number of breeding bouts per year as compared with contemporaries inhabiting the other s ite with low P. levior abundance. Reproductive patterns of the two pop ulations observed in the field accorded with the expectations of gener al life-history theory, and lent support to the hypothesis. However, l aboratory culture experiments revealed no evidence of a genetic basis for the interpopulation differences. The importance of establishing a genetic basis for the interpopulation divergence before invoking an ev olutionary explanation was discussed.