Taxonomic revision of Pimelodella (Siluriformes: Heptapteridae): an integrative proposal to delimit species using a multidisciplinary strategy

Abstract

The primary taxonomic research of Neotropical fishes still shows limited integration between morphological and molecular approaches, despite remarkable growth in both fields separately. If utilized in integrative fashion, they could successfully tackle groups which are traditionally considered intractable. Pimelodella Eigenmann & Eigenmann, 1888 is a perfect subject for the application of integrative taxonomic strategies. Pimelodella belongs to the family Heptapteridae and is distributed thorought trans- and cis-andean drainages, comprising one of the main components the ichthyofauna of small rivers. Currently, Pimelodella is the largest genus in the family, with 77 described species putatively considered as valid. However, the actual validity and delimitation of its species are troublesome due to their high diversity, broad distribution, conserved morphology and numerous incomplete descriptions. It is one of the greatest taxonomic bottlenecks in the systematics of neotropical fishes. This project proposes to conduct a taxonomic revision of Pimelodella using a morphological-molecular integrative approach. A classical taxonomic revision will embrace the entire diversity of the genus, with synonymies, examination of type-material, list of geographical records and all the components of that sort of study. The molecular component will be performed with a well-delimited set of Pimelodella species from Rio Madeira basin (a total of seven species, one of which yet undescribed), which have already been studied in detail by the proponent and which are represented by plenty of study material immediately available for both morphology and molecular data. A complete molecular study parallel to the morphological one would be impossible at the moment, as it would require collecting representative material throughout most of South America. At any rate, the species chosen for the multidisciplinary approach display enough diversity to allow for informative comparisons of molecular and morphological divergence estimations, providing a model of evaluation for the remaining species of the genus. The proposed study thus includes a complete taxonomic revision of Pimelodella, along with a comparison between morphological and molecular taxonomic resolution at the species-level, tested in a subset of the genus. (AU)