Molecular phylogeography of Oncomelania lindoensis (Gastropoda: Pomatiopsidae), the intermediate host of Schistosoma japonicum in Sulawesi

Abstract

Oncomelania lindoensis from Lake Lindu, Sulawesi, was characterized for genetic variation at 21 allozyme loci and compared with O. hupensis (China) and O. quadrasi (Philippines). Genetic distances and interpopulation patterns of allele-sharing point to a closer relationship between Sulawesi and the Philippines (Nei's unbiased genetic distances (D) averaged 0.50) than between Sulawesi and China (D = 0.79). These data, coupled with a consideration of the geographic distribution of the genus, support the hypothesis that the Sulawesi Oncomelania originated by avian-facilitated colonization from the Philippines about two million years ago. Oncomelania from Sulawesi were originally described as subspecifically distinct: Oncomelania hupensis lindoensis. However, the allopatric distribution, unique alleles at five loci, and significant genetic distances from congeners in Mindanao and elsewhere in the Philippines suggest that this taxon should be distinguished as a full species within the Oncomelania hupensis species group, name/y: O. lindoensis Davis and Carney 1973. Comparison with published data on variation within quadrasi and in three Chinese subspecies of hupensis showed that D values increase with taxonomic level in this species group. D averaged 0.15 (0-0.26) within Chinese subspecies and 0.04 (0-0.13) within the Philippines, but was 0.30 (0.20-0.45) between Chinese subspecies, and 0.48-0.80 between the three species (hupensis, quadrasi and lindoensis). The genotypic cluster species concept and these multilocus genetic distances can be used to help define species and subspecies in these medically important snails.