Evolution of Cambeva species (Siluriformes: Trichomycteridae): an approach iterating taxonomy, phylogeny, and historical biogeography.

Abstract

The Neotropical region is home of the richest freshwater ichthyofauna globally, a result of intrinsic evolutionary and geographical factors. he region’s fish fauna includes a remarkable diversity of catfishes, armored catfishes, and tetras. Within Siluriformes, the family Trichomycteridae is the second most diverse, comprising species commonly known as “candirus” and “cambeva”. In this context, Cambeva was recently described as a monophyletic and endemic group restricted to southern and southeastern Brazil. Currently, Cambeva includes 61 valid species, 17 of which occur in the Iguassu freshwater ecoregion. The region is considered a “hotspot” for the genus, and the high degree of endemism is linked to geological isolation, especially because of the Iguassu Falls, and tectonic events that shaped its landscape and your biodiversity. Despite recent taxonomic efforts, gaps remain in the understanding of phylogenetic relationships and species delimitation within Cambeva, especially in the Iguaçu River basin. Iterative taxonomy, which integrates molecular and morphological data, provides a robust framework for addressing these issues. Furthermore, to determine the causes of endemism in the region, historical biogeographic methods offer a better context for species distributions by integrating phylogenetic data with geomorphological processes such as vicariance, dispersal, and extinction. Accordingly, this study iteratively investigated the taxonomy, phylogeny, and biogeography of the genus Cambeva, with a focus on the Iguaçu ecoregion. A new species from the upper Iguaçu River is described; eight new species from the lower Iguaçu basin are proposed based on iterative taxonomy; a poorly known species from the Tietê River is reviewed and reclassified; and the phylogeny of the genus is reconstructed using molecular data to test biogeographic hypotheses explaining its current geographic distribution and endemism. Taken together, these studies provide new insights into the diversification of Cambeva, particularly within the Iguaçu ecoregion, and highlight the evolutionary role of geomorphological and hydrological processes in shaping freshwater fish diversity in the Neotropical region.