Genetic and morphological evidence cast doubt on the validity of Mexican troglobitic species of the Neotropical catfish genus Rhamdia (Siluriformes: Heptapteridae)

Abstract

Taxonomy and systematics Genetic and morphological evidence cast doubt on the validity of Mexican troglobitic species of the Neotropical catfish genus Rhamdia (Siluriformes: Heptapteridae) Evidencia genética y morfológica pone en duda la validez de las especies mexicanas troglobias del bagre neotropical del género Rhamdia (Siluriformes: Heptapteridae

Cave‐dwelling populations of Rhamdia (Siluriformes: Heptapteridae) from the Sierra de Zongolica, Veracruz, Mexico: an evidence‐based checklist with comments on their evolutionary history and taxonomy

“…Both the gene tree and the haplotype network are consistent with the expectations from geography, because the samples of R. laticauda most distant from the caves and from basins other than the Papaloapan (samples D04, MNCNGU-3, MNCN3499-MEX and MNCN653−MEX) are the most genetically divergent (Figure2).The observed phylogenetic/phylogeographic patterns, coupled with the lack of significant morphological differentiation, suggest that hypogean Rhamdia from the SdZ, including the nominal and currently recognized species R. zongolicensis, are either cave-adapted populations of the more widespread and epigean R. laticauda, or recently diverged species in very early stages of the speciation process. Research in this respect is on-going by the authors, and preliminary results, based on a larger character and taxon sampling, extend similar conclusions to the remaining three species of Mexican troglobitic Rhamdia (i.e., R. reddelli, R. macuspanensis and R. laluchensis)(Arroyave & De La Cruz Fernández, 2021). Notably, this would not be the first time that the validity of R. zongolicensis is brought into question.…”

“…Morphological variation among populations does not appear to be significant, particularly with respect to external meristic traits such as fin‐ray counts and in terms of overall body shape (Figure 1b); similarly, beyond troglomorphic traits, cave‐dwelling populations do not appear to differ considerably in external morphology from the epigean R. laticauda (Arroyave & De La Cruz Fernández, 2021). Furthermore, the authors’ observations confirm previous reports about the coexistence of individuals with varying degrees of troglomorphism (Mosier, 1984; Wilkens, 2001).…”

Neotropical sisterhood: new species ofGyrodactylusvon Nordmann, 1832 (Platyhelminthes: Monogenea) infectingRhamdia guatemalensisandRhamdia laticauda(Siluriformes: Heptapteridae) in Mexico

“…Neotropical freshwater catfishes from the genus Rhamdia are found throughout the Americas, from Mexico to Argentina. Rhamdia is taxonomically complex and no consensus exists on the total number of species that the genus contains, with hypotheses spanning a huge range, from 11 to 16 species (Silfvergrip, 1996; Perdices et al , 2002; Hernández et al , 2015; Arroyave & De La Cruz-Fernández, 2021). There is agreement, however, that the genus originated in South America and expanded northwards by colonizing Central America after the rise of the Isthmus of Panama – and stopped at the Isthmus of Tehuantepec in Mexico, the northernmost distribution limit for several Neotropical organisms.…”

“…There is agreement, however, that the genus originated in South America and expanded northwards by colonizing Central America after the rise of the Isthmus of Panama – and stopped at the Isthmus of Tehuantepec in Mexico, the northernmost distribution limit for several Neotropical organisms. This region between Tehuantepec and Panama corresponds to Tropical Middle America sensu Choudhury et al (2017), which is inhabited by two species of Rhamdia supported by morphometric and phylogenetic analyses, the pale catfish or ‘juil’, Rhamdia guatemalensis ; and the filespine ‘chulín’, Rhamdia laticauda (Perdices et al , 2002; Arroyave & De La Cruz-Fernández, 2021).…”