The Relationship between Heterozygosity for Enzyme Loci and Developmental Homeostasis in Peripheral Populations of Aquatic Bivalves (Unionidae)

Abstract

A distinct relationship between heterozygosity for enzyme loci and phenotypic variability is indicated; peripheral populations of 2 freshwater bivalve species from Nova Scotia, Canada, exhibit an increase in deviations from bilateral symmetry with a decrease in heterozygosity. Average heterozygosity over 5 polymorphic loci seems the strongest predictor of deviation from bilateral symmetry. Levels of heterozygosity which determine developmental homeostasis are different for the 2 spp. examined. Levels of heterozygosity detected electrophoretically are proposed to be indicative of overall levels of heterozygosity of the genome in these peripheral populations. Allelic depauperization detected electrophoretically is hypothesized to be due mainly to founder events, which are proposed to affect all susceptible loci equally.