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.

Comparative Osteology, Phylogeny and Classification of the Eastern South American Catfish Genus Trichomycterus (Siluriformes: Trichomycteridae)

“…Furthermore, this study has shown that osteological characters combined with molecular data may be useful to consistently delimit and distinguish between trichomycterine groups that cannot be properly distinguished using only external morphological features. More importantly, this integrative approach sheds light upon the way of solving still persistent problems in trichomycterine systematics, including a formal generic placement for the numerous Andean and Guianan incertae sedis taxa [9,31,78].…”

New records of native and introduced fish species in a river basin of Western Ecuador, the Chocó-Darien Ecoregion, using DNA barcoding

“…The systematics of Astroblepus in Ecuador is not completely understood and regional efforts still lack Ecuadorian samples [21]. For Trichomycterus, our samples cluster with Colombian species but species from Ecuador are still absent from large-scale studies [63]. Trichomycterus specimens did show genetic variability (S5 Fig in S1 File), where the ones used in the tree exhibited genetic divergence and morphological examination corroborated this by separating them in two sympatric species: T. aff banneaui and Trichomycterus sp1.…”

Phylogenetic position of Trichomycterus astromycterus (Siluriformes: Trichomycteridae), an enigmatic trichomycterid from eastern Brazil, inferred from molecular data

“…The Trichomycterinae is the most diverse subfamily of the Neotropical catfish family Trichomycteridae, comprising over 250 valid species that occur in most freshwater habitats of South America (Costa et al ., 2021a). Nonetheless, monophyly and intra‐subfamilial relationships have been established only in recent years, after the inclusion of molecular data in phylogenetic analyses (Costa et al ., 2021a; Fernandez et al ., 2021; Katz et al ., 2018; Ochoa et al ., 2017, 2020). On the contrary, numerous trichomycterine taxa still have their phylogenetic position uncertain, and some others have been incorrectly placed due to a weak classification at the genus level and uncertainty of generic boundaries (Costa et al ., 2021b).…”