Molecular Phylogeography of Oncomelania Lindoensis (Gastropoda: Pomatiopsidae), the Intermediate Host of Schistosoma Japonicum in Sulawesi

Oncomelania lindoensis from Lake Lindu, Sulawesi, was characterizedfor geneticvariation at 21 allozyme loci and compared withO. hupensis (China) and O.quadrasi (Philippines). Geneticdistances and interpopulation patterns of allele-sharingpointto a closer relationship between Sulawesi and the Philippines(Nei's unbiased geneticdistances (D) averaged 0.50) than betweenSulawesi and China (D=0.79). These data, coupled with a considerationof the geographic distribution of the genus,support the hypothesisthat the Sulawesi Oncomelaniaoriginated by avian-facilitatedcolonizationfrom the Philippines about two million years ago. Oncomelania from Sulawesi were originally described as subspecificallydistinct: Oncomelania hupensis lindoensis. However, the allopatricdistribution, unique alleles atfive loci, and significant geneticdistances from congeners in Mindanao and elsewhere in thePhilippinessuggest that this taxon should be distinguished as a full specieswithin the Oncomelania hupensis species group, namely: O. lindoensisDavis & Carney 1973.Comparison with published data on variationwithin quadrasi and in three Chinesesubspecies of hupensisshowed that D values increase with taxonomic level inthis speciesgroup. D averaged 0.15 (0–0.26) within Chinese subspeciesand 0.04 (0–0.13) within the Philippines, but was 0.30(0.20–0.45) between Chinesesubspecies, and 0.48–0.80between the three species (hupensis, quadrasi andlindoensis).The genotypic cluster species concept and these multilocus geneticdistancescan be used to help define species and subspeciesin these medically important snails. (Received 14 May 1997; accepted 20 April 1998)