Parasite (Schistosoma mansoni) and host (Biomphalaria glabrata) genetic diversity: population structure in a fragmented landscape

Random amplified polymorphic DNA (RAPD) markers were used to quantify genet ic diversity within and between 5 populations of Schistosoma mansoni within its definitive host (Rattus rattus) and the 5 corresponding populations of the snail intermediate host (Biomphalaria glabrata) from a limited endemic area of murine schistosomiasis on the island of Guadeloupe. Analysis of mo lecular variance (AMOVA) and canonical correspondence analysis (CCA) were u sed to test the significance of genetic differentiation between populations . Both methods gal-a similar results. Of total gene diversity, 15.1% (AMOVA ) and 18.8% (CCA) was partitioned between localities for S. mansoni with an absence of association between genetic and geographical distances. Geograp hical localities accounted for 20.5% (CCA) of the total diversity for B. gl abrata populations. The genetic distances between pairs of parasite populat ions were not correlated with the genetic distances between the correspondi ng pairs of snail host populations. Such strong patterns of local different iation of both parasite and snail populations are consistent with predictio ns based on metapopulation dynamics and ma) have implications on host-paras ite susceptibility. relationship through local adaptation processes.