Emerging patterns in phylogenetic studies of trichomycterid catfishes (Teleostei, Siluriformes) and the contribution of Andean diversity

Abstract

Consensus is emerging among studies using DNA sequence data addressing problems in the taxonomy and relationships of trichomycterid catfishes, a dominant component of the Neotropical freshwater ichthyofauna, that have heretofore eluded efforts based on morphological data alone. No previous studies using molecular data have included representatives of Hatcheria and Silvinichthys, and none have included dense representation of the diverse Andean species of Trichomycterus. This study assembled both available and novel comparative DNA sequence data inclusive of Hatcheria, Silvinichthys, and additional Trichomycterus species not represented in previous studies to form the most taxonomically comprehensive molecular dataset of the Trichomycterinae at the genus level to date. Our results confirm previous findings of strong support for a monophyletic subfamily Trichomycterinae while rejecting the monophyly of its most diverse genus, Trichomycterus. Our results do not corroborate Trichomycterinae split into two reciprocally monophyletic groups, and we show strong support for a sister-group relationship between Eremophilus mutisii and Trichomycterus bogotensis that suggests some degree of evolutionary distinctiveness for this clade of Colombian-endemic species. Within Trichomycterus, we uncovered a novel clade of central Andean species and reveal a close relationship among southern Andean taxa that included a non-monophyletic Silvinichthys, Bullockia, Hatcheria, plus a number of Trichomycterus species. Our results are broadly congruent with recent studies that have uncovered rampant polyphyly within the genus Trichomycterus and provide emerging evidence, as a result of increased taxonomic representation, for geographically circumscribed subclades of Trichomycterus species. Nevertheless, the widespread low support and resolution at most basal nodes pose a considerable challenge in understanding major patterns of intergeneric relationships, which in turn hinders our efforts to shed critical light on the biogeographic history of the group.