A DNA sequence-based study of theSchistosoma indicum(Trematoda: Digenea) group: population phylogeny, taxonomy and historical biogeography

Abstract

SUMMARYPartial (DNA) sequences were collected for 2 mitochondrial loci (SrrnaandLrrna, therrnS andrrnL rRNA genes respectively) forSchistosoma indicumgroup species from 4 Southeast Asian countries. The samples included 7 populations, 4 of which were previously unstudied. In 11 cases the combination of locus and population was new. The aim of the study was to provide a phylogeny based on new independent data and multiple populations (earlier studies had mostly used a common set of field samples or laboratory lines) and to examine interrelationships and phylogeography within this species group. Paraphyly of theS. indicumgroup was confirmed, as was the basal position ofSchistosoma incognitumin theSchistosomaphylogeny. Southeast AsianSchistosoma spindaleandS. incognitumpopulations were shown to fall into their respective con-specific cohesive groupings. Estimated divergence times for these taxa were shown to be related to Pleistocene changes in sea level and the radiation of definitive host groups. A revised phylogeographical model is proposed in the light of these findings.