State of the art in taxonomy of Chilean freshwater bivalves: advances and difficulties
- An update of the Chilean freshwater bivalve taxonomy is presented. The bivalves described at present are adscribed to two families: Hyriidae represented only by the genus Diplodon with two species (D. chilensis and D. solidulus) and Sphaeriidae represented by three genera: Pisidium with seven species (P. chilense, P. magellanicum, P. lebruni, P. observationis, P. meierbrooki, P. huillichum and P. llanquihuense), Sphaerium with two species (S. lauricochae and S. forbesi), and Musculium with two species (M. argentinum and M. patagonicum). Sub-generic and sub-specific taxa are recognized for Hyriidae only. The present study includes the synonymy, type locality and geographic distribution where the species have been recorded. The most reliable diagnostic features for Hyriidae species identification are the hinge morphology in adult specimens, the presence or absence of the valve teeth, and their position and shape in larvae. At the generic level within Sphaeriidae, the most reliable taxonomic characters are the morphology and number of the siphons, and the size of both demibranchs. At the species level these characters are valve morphometry and morphology, which includes beak position, hinge features, shape and size of cardinal teeth, valve sculpture and pore density of the inner surface of valves. Results are discussed regarding advances and conflicts related to the taxonomic and systematic arrangement in both families, the difficulties in data compilation, the need to re-describe some species using cytogenetic and molecular techniques, and to increase this database with new records in geographic areas not yet studied. Pisidium chilense, P. huillichum, P. llanquihuense and P. lebruni are proposed as endemic species for Chile and zoogeographic regions are sketched based on the distribution of Chilean spheriids reported at the present.