New combinations and typification of Neotropical Cosmioneis species (Cosmioneidaceae)

The identity of Navicula brasiliana (Cleve) Cleve is here detailed based on analysis of the original slide from the Cleve & Moller collection. Additional observations with light and scanning electron microscopy of two later varieties described from the Neotropics are also provided: N. brasiliana var. platensis Frenguelli and N. brasiliana var. guadalupensis Manguin described from Argentina and Guadalupe (French Antilles), respectively. Based on the morphological characteristics of the frustules the three taxa belong to Cosmioneis D.G. Mann & Stickle. These rather rare taxa are usually reported from fresh to brackish water environments, including hot springs in the Neotropical and Paleotropical regions. While N. brasiliana var. platensis is widely recorded in several regions of the African continent and Argentina, N. brasiliana is often recorded in Central America, almost certainly because of uncertainty over their identities, to date based only on line drawings. We conclude that Cosmioneis brasiliana (Cleve) C.E. Wetzel & Ector comb. nov. is a distinct species, while N. brasiliana var. guadalupensis is a taxonomic synonym of Cosmioneis platensis (Frenguelli) C.E. Wetzel, E. Sar & Ector comb. nov.