Page last updated
11 November 2014
Unionoida cum Grano Salis
Neotropica includes all of South America, north through Central America to the Mexican Plateau. The region is inhabited by 217 species in four families: Unionidae, Hyriidae, Mycetopodidae and Etheriidae.
The Mesoamerica Subregion (NT1; 102 spp.) includes Central America to the Isthmus of Panama. The fauna consists largely unioinid genera, and presumably those various lineages had their origins in the Nearctic Region. We regard Mesoamerica as part of the Neotropical Region due to the observed degree of genus-level endemism.
The remainder of the subregions are portions of South America proper. The Transandean Subregion (NT2; 13 spp.) is the area between the Isthmus of Panama and the Andes Mountains in the northwest. The Amazonas-Orinoco Subregion (NT3; 61 spp.) includes the entire Amazon and Orinoco basins as well as the Guyanas. The Atlantic coastal streams (including the São Francisco) in eastern Brazil comprise the Atlantic-São Francisco Subregion (NT4; 21 spp.). The Paraná-Paraguay Subregion (NT5; 65 spp.) is composed of all the rivers draining via the Rio de la Plata and the coastal streams of Uruguay and southern Brazil. Finally, three species occur in the Patagonia Subregion (NT6).