História evolutiva de espécies do gênero Potamotrygon Garman, 1877 (Potamotrygonidae) na Bacia Amazônica

Abstract

The ancestors of the family Potamotrygonidae have adapted to freshwater environment about 20 millions years before present, colonizing the continental South America from the Caribbean region. Since then, the group has radiated to about 20 species classified in three genera. In the present study it was demonstrated that the species Plesiotrygon iwamae, Potamotrygon sp.1 and P. schroederi, which represent the root of the potamotrigonid radiation, have diverged within a short period of time around 7 millions years before present. The origin of the majority of the species of the genus Potamotrygon, here denominated roseta-ocelado group, a complex of at least six species, has begun in the last 2 millions years before present. This diversification has occurred extremely rapidly, which makes the reconstruction of the phylogenetic relationships among these species very difficult. The recent and rapid origin of the species of the roseta-ocelado group is probably related to the breach of the Purus Arch by the ancestral of the group, followed by the colonization of Amazonas River tributaries of eastern Amazônia and their isolation which most likely was caused by changes in water level caused by climatic oscillations in Pleistocene. Phylogeographic and population genetic analyses demonstrated the existence of at least five distinct evolutionary lineages when the species Potamotrygon motoro, P. orbignyi e P. scobina were analyzed together. These distinct lineages occur in tributaries of middle and lower Amazonas River, all more closely related to P. motoro. There is a strong association between haplotypes and geographic localities, and replicated color patterns in different lineages found at different geographic localities. As currently defined, Potamotrygon orbignyi is polyphyletic and should be taxonomically revised. The application of DNA barcoding methodology to species of the family Potamotrygonidae is only valid for assignment of specimens to its species, with exception of the species of the complex P. motoro, P. orbignyi and P. scobina which share haplotypes extensively. However, the barcoding methodology is not valid for the identification of new species which should be done in conjunction with other information.