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

Four of the 7 species of Rhamdia present in Mexico stand out for being microendemic and also troglobitic, that is, for being restricted to their type-locality caves and for exhibiting a distinctive phenotype characterized by ocular reduction/loss and body depigmentation. Diagnosis and recognition o...

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Main Authors: Jairo Arroyave, Dalia Angélica De La Cruz-Fernández
Format: Article
Language:English
Published: Universidad Nacional Autónoma de México 2021-08-01
Series:Revista Mexicana de Biodiversidad
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Online Access:https://revista.ib.unam.mx/index.php/bio/article/view/3718
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author Jairo Arroyave
Dalia Angélica De La Cruz-Fernández
author_facet Jairo Arroyave
Dalia Angélica De La Cruz-Fernández
author_sort Jairo Arroyave
collection DOAJ
description Four of the 7 species of Rhamdia present in Mexico stand out for being microendemic and also troglobitic, that is, for being restricted to their type-locality caves and for exhibiting a distinctive phenotype characterized by ocular reduction/loss and body depigmentation. Diagnosis and recognition of Mexican troglobitic forms as distinct species, however, appears to be primarily based on their regressive troglomorphic phenotype and highly localized geographic distributions. To test the adequacy of its current taxonomy, we investigated patterns of genetic and phenotypic variation in Mexican troglobitic Rhamdia in a phylogenetic context. Our results indicate that external morphology does not allow for unambiguous differential diagnoses and robust distinction among troglobitic species. Similarly, beyond typical regressive troglomorphic traits, troglobitic species do not differ greatly in external morphology from their most closely related congener, the epigean species Rhamdia laticauda. From a phylogenetic perspective, continued recognition of troglobitic species implies a deep and generalized paraphyly in R. laticauda. Despite the evidence presented herein, we refrain from making nomenclatural decisions until we can unambiguously ascertain that our findings are indeed explained by phylogeographic structure in R. laticauda, instead of by recent divergence and subsequent speciation of cave-dwelling lineages from this widespread epigean species.
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spelling doaj-art-3561aa30bbb948efa0cca41b25064aed2025-08-20T02:58:51ZengUniversidad Nacional Autónoma de MéxicoRevista Mexicana de Biodiversidad1870-34532007-87062021-08-019210.22201/ib.20078706e.2021.92.3718Genetic and morphological evidence cast doubt on the validity of Mexican troglobitic species of the Neotropical catfish genus Rhamdia (Siluriformes: Heptapteridae)Jairo Arroyave0Dalia Angélica De La Cruz-Fernández1Universidad Nacional Autónoma de MéxicoUniversidad Nacional Autónoma de México Four of the 7 species of Rhamdia present in Mexico stand out for being microendemic and also troglobitic, that is, for being restricted to their type-locality caves and for exhibiting a distinctive phenotype characterized by ocular reduction/loss and body depigmentation. Diagnosis and recognition of Mexican troglobitic forms as distinct species, however, appears to be primarily based on their regressive troglomorphic phenotype and highly localized geographic distributions. To test the adequacy of its current taxonomy, we investigated patterns of genetic and phenotypic variation in Mexican troglobitic Rhamdia in a phylogenetic context. Our results indicate that external morphology does not allow for unambiguous differential diagnoses and robust distinction among troglobitic species. Similarly, beyond typical regressive troglomorphic traits, troglobitic species do not differ greatly in external morphology from their most closely related congener, the epigean species Rhamdia laticauda. From a phylogenetic perspective, continued recognition of troglobitic species implies a deep and generalized paraphyly in R. laticauda. Despite the evidence presented herein, we refrain from making nomenclatural decisions until we can unambiguously ascertain that our findings are indeed explained by phylogeographic structure in R. laticauda, instead of by recent divergence and subsequent speciation of cave-dwelling lineages from this widespread epigean species. https://revista.ib.unam.mx/index.php/bio/article/view/3718Rhamdia reddelliRhamdia zongolicensisRhamdia macuspanensisRhamdia laluchensisTroglomorphismCave fishes
spellingShingle Jairo Arroyave
Dalia Angélica De La Cruz-Fernández
Genetic and morphological evidence cast doubt on the validity of Mexican troglobitic species of the Neotropical catfish genus Rhamdia (Siluriformes: Heptapteridae)
Revista Mexicana de Biodiversidad
Rhamdia reddelli
Rhamdia zongolicensis
Rhamdia macuspanensis
Rhamdia laluchensis
Troglomorphism
Cave fishes
title Genetic and morphological evidence cast doubt on the validity of Mexican troglobitic species of the Neotropical catfish genus Rhamdia (Siluriformes: Heptapteridae)
title_full Genetic and morphological evidence cast doubt on the validity of Mexican troglobitic species of the Neotropical catfish genus Rhamdia (Siluriformes: Heptapteridae)
title_fullStr Genetic and morphological evidence cast doubt on the validity of Mexican troglobitic species of the Neotropical catfish genus Rhamdia (Siluriformes: Heptapteridae)
title_full_unstemmed Genetic and morphological evidence cast doubt on the validity of Mexican troglobitic species of the Neotropical catfish genus Rhamdia (Siluriformes: Heptapteridae)
title_short Genetic and morphological evidence cast doubt on the validity of Mexican troglobitic species of the Neotropical catfish genus Rhamdia (Siluriformes: Heptapteridae)
title_sort genetic and morphological evidence cast doubt on the validity of mexican troglobitic species of the neotropical catfish genus rhamdia siluriformes heptapteridae
topic Rhamdia reddelli
Rhamdia zongolicensis
Rhamdia macuspanensis
Rhamdia laluchensis
Troglomorphism
Cave fishes
url https://revista.ib.unam.mx/index.php/bio/article/view/3718
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