The genetic population structures of the freshwater snail Bulinus globosus and its trematode parasite Schistosoma
haematobium from 8 river sites in the Zimbabwean highveld were compared using randomly amplified DNA(RAPD) markers.
There was significant variability between snail populations collected at different sites, but schistosome populations only
showed differentiation at a wider geographical scale (between 2 non-connected river systems). For snails, genetic distance
was better correlated with proximity along rivers than absolute geographical separation. In contrast, schistosome genetic
distance was better correlated with absolute geographical separation than proximity along rivers. These results are
consistent with different dispersal mechanisms for snails and schistosomes and the implications
for host–parasite coevolution are discussed.
SELF-FERTILIZATION VERSUS CROSS-FERTILIZATION IN THE HERMAPHRODITIC FRESHWATER SNAIL BULINUS GLOBOSUS