Abstract. It has been suggested that the patchy distribution of snail susceptibility to schistosomes might be due to genetic drift. Since direct estimation of genes for susceptibility is not feasible in population studies, electrophoretic techniques were used to examine this hypothesis for populations of Biomphalaria glabrata from Puerto Rico. These populations were characterized by relative genetic homogeneity within populations and differentiation among local populations. The data presented are consistent with the hypothesis that random genetic drift and low rates of migration might be responsible for the patchy distribution of snail susceptibility to schistosomes.
Present address: Department of Biology, C-016, University of California, San Diego, La Jolla, California 92093.