Systematics of the Neritilia rubida complex (Gastropoda: Neritiliidae): Three amphidromous species with overlapping distributions in the Indo-Pacific

Abstract

Re-examination of more than 7,000 gastropod specimens previously assigned to Neritilia rubida (Pease, 1865) or Neritilia consimilis (von Martens, 1879) from streams and rivers in the tropical and subtropical Indo-Pacific revealed three species: N. rubida, N. vulgaris new species, and Platynerita rufa new genus and new species. Neritilia consimilis from Mauritius is synonymized under N. rubida, the latter originally described from Tahiti. The three species herein recognized have extensive, largely overlapping distributions centred in the west Pacific: N. rubida ranges from Madagascar to French Polynesia, N. vulgaris from Madagascar to Samoa, and P. rufa from the Philippines to French Polynesia. Conchological and anatomical traits indicate that the three species are a polyphyletic group and that N. rubida is more closely related to N. succinea (Récluz, 1841) and N. manoeli (Dohrn, 1866), both in the Atlantic, rather than to the sympatric N. vulgaris. We suggest that their larval dispersal capabilities across the ocean have hindered the geographic isolation of populations and that ecological segregation may have played a more important role in genetic differentiation and speciation in freshwater neritiliids.