Genetic differentiation, pelagic larval transport and gene flow between local populations of the intertidal marine mollusc Adalaria proxima (Alder & Hancock)

It has been widely assumed that the existence of a pelagic larval phase in the life cycle of many sedentary/sessile species of marine invertebrate facilitates large-scale dispersal potential and results in gene flow between populations. Population genetic evidence presented here, for an intertidal nudibranch mollusc (which displays a pelagic lecithotrophic larva), shows considerable spatial heterogeneity over relatively short geographical distances (approximate to 3 km). This genetic heterogeneity was temporally stable between three succeeding generations. The data are interpreted as indicating that actual larval transport (and hence gene flow) is considerably abbreviated over that which might be expected on the basis of larval culture data alone.