Phylogenetic relationships of a new catfish of the genus Trichomycterus (Siluriformes, Trichomycteridae) from the Brazilian Cerrado, and the role of Cenozoic events in the diversification of mountain catfishes

Abstract

The Brazilian Cerrado highlands shelter the headwaters of the three largest South American hydrographic basins, where a great species diversity is concentrated, but some biological groups are still insufficiently known. The focal taxa of this study are trichomycterid catfishes of the subgenus Cryptocambeva, genus Trichomycterus, endemic to mountain areas of south-eastern Brazil. The primary objective of this study is to test through a molecular phylogeny if a new species collected in streams of the upper Rio Paraná basin draining the Serra da Canastra is sister to T. macrotrichopterus, endemic to the upper Rio São Francisco at another facet of the Serra da Canastra, as suggested by morphological data. The analysis corroborated sister group relationships between these two species, besides supporting four main clades in Cryptocambeva, each of them endemic to distinct mountain regions. A time-calibrated analysis supported the divergence timing between the new species and T. macrotrichopterus at the Pliocene, which is chronologically compatible with the final period of intense fluvial configuration re-arrangement, when São Francisco headwater streams were captured by the Paraná basin. The new species herein described is similar to T. macrotrichopterus and distinguished from all other species of Cryptocambeva by having a long pectoral-fin filament. These two species are distinguished from each other by characteristics of the latero-sensory system, colour pattern and bone morphology.