For marine animals with the capacity of producing large number of offsprings and high average mortalities of early life stages, there exists the potential for a large variance in the success with which individual contribute offspring to the next generation of reproducing adults. For these animals, an assumption of binomial variance in offspring numbers is likely wrong, and that a small minority of offsprings may replace an entire population in each generation when there is a mismatch between reproductive activity and permissive oceanographic conditions. To examine this hypothesis, a model oyster population Crassostrea gigas in Dabob Bay, WA, for which a 30-year record exists on reproductive activity and recruitment success, will be tested rigorously by comparison of genetic diversity among larvae, juveniles, and adults. Genetic diversity studies of larval populations are now made possible by advances in molecular biology. Large variance in reproductive success may be a major factor in the population biology, adaptation and speciation of most marine animals.
