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

Abstract

The results of this study indicate a distinct relationship between heterozygosity for enzyme loci and phenotypic variability; peripheral populations of two fresh-water bivalve species from Nova Scotia, Canada, exhibit an increase in deviations from bilateral symmetry with a decrease in heterozygosity. Average heterozygosity over five polymorphic loci seems the strongest predictor of deviation from bilateral symmetry. Levels of heterozygosity which determine developmental homeostasis are different for the two species 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.