GENETIC STRUCTURE OF KENYAN POPULATIONS OF BIOMPHALARIA PFEIFFERI (GASTROPODA: PLANORBIDAE)

Abstract

Biomphalaria Pfeifferi is widespread in Africa, tolerates a diverse array of habitats, and is highly susceptible to schistosome infection. As such, it is the most important host of Schistosoma mansoni in the Old World. Representatives of Biomphalaria pfeifferi from twelve localities in southern Kenya were examined using starch gel electrophoresis in order to describe the population structure. Ten to fifteen loci were resolved in each population. Genotypic frequencies obtained for 10 loci have been used to calculate Nei' genetic distances. Nine eastern populations were relatively similar to each other (D ≤ 0.016), but divergent from western populations (D ≤ 0.178). Two of three western populations were quite similar (D = 0.001), the third being more divergent (D ≤ 0.258). Genotypic frequencies showed a substantial departure from Hardy-Weinberg equilibrium, due to a marked deficiency of heterozygotes. Calculation of F-statistics revealed evidence of non-random mating as well as considerable differentiation among localities. Biomphalaria pfeifferi differs from other Biomphalaria species studied to date in exhibiting evidence of non-random mating. Higher levels of inbreeding could alter the pattern of response to selection imposed by parasites such as Schistosoma mansoni.