Taxonomy of Poptella compressa (Günther 1864) (Characiformes: Characidae: Stethaprioninae): a widely distributed taxon or hidden diversity?

• Grant number: 23/00152-7
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2023
• End date: May 31, 2024
• Field of knowledge: Biological Sciences - Zoology - Taxonomy of Recent Groups
• Principal Investigator: Ricardo Cardoso Benine
• Grantee: Anna Luiza Nardi Câmara
• Host Institution: Instituto de Biociências (IBB). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

The remarkable diversity of Neotropical freshwater fish species reinforces the need for urgent studies to describe their biodiversity, ecology, and evolutionary biology. Despite the constant increase in our knowledge of this ichthyofauna, new discoveries, as well as groups that are still poorly understood taxonomically, require attention. Recently, the subfamily Stethaprioninae was redefined, resizing it as a more inclusive clade that encompasses several genera of characids grouped into four tribes. Within the tribe Stethaprionini the "Clade Stethaprion" refers to an earlier definition of the Stethaprioninae, a monophyletic group formed by the genera Stethaprion, Brachychalcinus, Poptella, and Orthospinus and diagnosed from other characids by the presence of a predorsal spine articulated to the first ray of the dorsal fin. The genus Poptella is distinguished from the other genera of the subfamily by the shape of the predorsal spine, in which its anterior end is rounded and concave, with two pointed projections directed posteriorly, like a saddle. Poptella comprises six valid species: P. brevispina, P. compressa, P. longipinnis and P. paraguayensis, P. actenolepis and P. fuscata. Recently, the existence of seven new species was indicated: Poptella sp.1, Poptella sp.2, Poptella sp.3 (Araguaia-Tocantins river basin), Poptella sp.4 (Juma river basin - species already described: Poptella actenolepis ), Poptella sp.5 (Xingu river basin), Poptella sp.6 (Acre river basin) and Poptella sp.7 (Purus river basin). In recent years, several local populations similar to P.compressa have been collected in regions such as the Upper Amazon, Peru, Colombia, and Ecuador, as well as in the central Amazon of Brazil. Although all these populations are being identified as P. compressa, there are differences in pre-dorsal spine size and shape suggesting that these local populations may be new species. For this reason, the objective of this project is to study the variation of the pre-dorsal spine of Poptella compressa and verify if there are consistent forms that allow its characterization as species.