Electrophoretic differentiation of two Halipegus (Trematoda: Hemiuridae) congeners in an amphibian population.

The presence of Halipegus eccentricus, which previously had been absent from a study area, was confirmed when marked genetic differences were observed within what had been thought to be a homogenous population of Halipegus occidualis from the buccal region of the green frog, Rana clamitans. Starch gel electrophoresis was used to determine levels of genetic variation in H. occidualis and H. eccentricus. The H. occidualis population had 12% polymorphic loci and average individual heterozygosity of 0.05. Endemism of snail hosts, limited potential for parasite immigration, monoecious adults, and asexual reproduction occurring in the molluscan intermediate host may be factors that minimize the extent of genetic variability in the parasite population.