Barcoding Fishes of Argentina: The Progress of the Freshwater Campaign.

ROSSO, J.J.; MABRAGAÑA, E.; GONZÁLEZ CASTRO, M.; DÍAZ DE ASTARLOA, J. M.

Conferencia; Fourth International Barcode of Life conference.; 2011

Abstract Historically, the identification of species was largely based on morphological characters. In recent years an innovative molecular technique using a fragment of mitochondrial DNA has proved to be useful for this purpose in many taxa. The application of such a technique is particularly important when approaching a species diversity analysis over a wide geographic area. Species occupying large geographic areas may display different genetic lineages and might mask isolated populations with a genetic divergence at the species level. This may probably be the case for the freshwater fish fauna of Argentina. Argentina is the 8th larger country in the world. It covers 3,694 kilometres from north to south and 1,423 from west to east. Its territory extends more than 33 latitude degrees. The freshwater fish fauna of Argentina comprises more than 450 species. Up to now, the campaign to barcoding these species surveyed 57 different environments encompassing 5 of the 11 ichthyogeographic provinces. Almost 600 specimens from more than 100 species were collected. This represents more than 20% of the known ichthyofauna. Our first results demonstrate that barcoding is an efficient tool for species identification of freshwater fishes of the Pampa Plain, Argentina. Based on the neighbour-joining trees, all members of a given genera clustered within the same clade. The mean conspecific, congeneric and confamiliar genetic distances were 0.6%, 9.1% and 20.2% respectively. The use of COI sequences (n=195) from 37 putative species allowed us to further discriminate among 34 species. This means that molecular species identification was in concordance with current taxonomical classification in 92% of cases. Moreover, preliminary analysis of released sequences in our project suggest the existence of intra-specific groups. Clades of species such as Cnesterodon decemmaculatus, Bryconamericus iheringii and Salminus brasiliensis showed individuals with a divergence of 2.4, 5 and 6 % from its conspecifics. Several aspects of the taxonomy of conflicting groups could be further untangled with forthcoming COI sequences. Particularly, the existence of species complex in Hoplias malabaricus, Synbranchus marmoratus, Astyanax fasciatus and Australoheros facetus as well as morpho-species in Oligosarcus jenynsii could be explored. Presently, the contrasting results between the meristic, morphometric and landmark-based morphometry and partial results of the whole set of COI sequences of Oligosarcus jenynsii suggest that this species would present significantly distinct morphos.