POPULATION-GENETICS AND GENETIC-VARIABILITY OF BULINUS-GLOBOSUS (GASTROPODA, PLANORBIDAE) FROM THE 2 MAIN RIVER SYSTEMS IN ZIMBABWE

Bulinus globosus is the only known vector of Schistosoma haematobium i n Zimbabwe, The population genetic structure of this vector snail from the two main river drainage systems, represented by 27 localities, wa s determined from starch gel isoenzyme electrophoretic data, Out of 11 enzyme systems screened eight loci were resolved, and six of them wer e polymorphic in at least one of the populations sampled, Genotypic di stributions showed deviations from Hardy-Weinberg proportions due to d eficiency of heterozygotes and this was attributed to selfing, The Sav e River drainage system, which falls under the high rainfall area, rev ealed a higher proportion of gene diversity than the Sanyati River dra inage system, Hierarchical analysis showed that differentiation within the populations in the two drainages (F-SR = 0.085) was higher than b etween the two drainages (F-RT = 0.011), This highlights the role of e cological factors (drought/desiccation and floods), genetic drift, and seasonal gene flow as the main factors influencing the genetic struct ure of these populations.