Leucine aminopeptidase variation and fitness parameters in the estuarine bivalve Geukensia demissa

Investigations into several potential fitness parameters in collections of the estuarine bivalve Geukensia demissa (Dillwyn), (from Newport Bay and Alamitos Bay in southern California, conducted from 1981 to 1984) under both field and laboratory conditions, revealed differences in growth rate, tissue weight, and mortality which were correlated with leucine aminopeptidase-1 (LAP-1) genotype. The results of these fitness studies are consistent among themselves and with the results of previous population genetic studies on G. demissa. As a whole, these studies suggest that differential fitness among LAP-1 genotypes in conjunction with a variable environment act to maintain the LAP-1 polymorphism in natural populations of this species.