Host-parasite population genetics: a cross-sectional comparison of Bulinusglobosus and Schistosoma haematobium

The genetic population structures of the freshwater snail Bulinus globosus and its trematode parasite Schistosoma haematobium from 8 river sites in th e Zimbabwean highveld were compared using randomly amplified DNA (RAPD) mar kers. There was significant variability between snail populations collected at different sites, but schistosome populations only showed differentiatio n at a wider geographical scale (between 2 non-connected river systems). Fo r snails, genetic distance was better correlated with proximity along river s than absolute geographical separation. In contrast, schistosome genetic d istance was better correlated with absolute geographical separation than pr oximity along rivers. These results are consistent with different dispersal mechanisms for snails and schistosomes and the implications for host-paras ite coevolution are discussed.