A Riverine Species Flock? A Remarkably High Diversity of Endemic Fossorial Catfishes, Genus Cambeva (Siluriformes: Trichomycteridae), in a Small Mountain Drainage of Southern Brazil

A field inventory in the Rio Chapecó drainage, southern Brazil, about 11,120 km2, revealed an unexpected diversity of endemic small fossorial catfishes, genus Cambeva, comprising 2 species recently described and 11 undescribed. They were found in different habitats, including sediment types and altitudes, and exhibited great morphological diversity, suggesting them to be a species flock. The objectives of this study were to analyse criteria (monophyly, endemicity, species richness, ecomorphological diversity) used to recognise species flocks and to describe the new species, which were diagnosed using external morphology and osteological characters. The phylogenetic analyses using COI, CYTB and RAG2 (2305 bp) for 64 species of Cambeva and 4 outgroups did not support that species assemblage as a single monophyletic group but supported a clade with 3 species, the C. alphabelardense clade, and a clade with 10 species, the C. betabelardense clade. The latter clade was recognised as a putative species flock based on those criteria. A time-calibrated analysis indicated the origin and diversification of both clades during the Miocene, a timeframe coinciding with the emergence and persistence of the Paranean Sea, which may have isolated adjacent river drainages, favouring the high species diversification of Cambeva, besides diversification of the Crenicichla missioneira complex from the same region.