Phylogeny of the Neotropical genus Gephyrocharax (Characiformes: Characidae: Stevardiinae), with remarks on the tribe Stevardiini

Abstract

Stevardiinae, which consists of 326 species and 44 genera, is a monophyletic subfamily within the family Characidae. In a recent classification of the subfamily, the tribe Stevardiini was expanded from three (Corynopoma, Gephyrocharax and Pterobrycon) to six genera by the addition of Chrysobrycon, Hysteronotus and Pseudocorynopoma. However, no morphological evidence has supported this definition of the tribe and the monophyly of Gephyrocharax. To address these issues, a phylogenetic study of most stevardiins focusing on Gephyrocharax was conducted. A data matrix including 532 characters and 213 taxa (73 stevardiines, 19 of which were stevardiins) was processed using maximum parsimony in TNT 1.5. All characters were analysed under extended implied weighting, exploring 21 k values. A strict consensus (comprising the most stables trees obtained) was used as the final topology. The results support the current definition of Stevardiini, as well as the monophyly of Chrysobrycon, Gephyrocharax and Pterobrycon. Corynopoma was obtained as the sister group of Gephyrocharax, the latter being phylogenetically diagnosed by two synapomorphies associated with caudal-fin morphology of adult males. The following interspecific relationships within Gephyrocharax are hypothesised: (G. martae ((G. chocoensis (G. major (G. atracaudatus, G. intermedius))) (G. venezuelae (G. sinuensis (G. valencia (G. caucanus (G. melanocheir, G. torresi)))))))).

Phylogenetic relationships of a new genus and species of stevardiine fish (Characiformes: Characidae: Stevardiinae) from the Río Amazonas basin, Peru

“…To test the phylogenetic position and relationships of the new taxa within Characidae and Stevardiinae, two different and comprehensive previously published data sets were used: (A) the combined morphological and molecular matrix by Mirande () and (B) the morphological matrix by Vanegas‐Ríos (). The data set A included 859 species, composed of 6,653 characters: 520 morphological and eight molecular markers composed of four mitochondrial ( cytochrome c oxidase subunit I [ COI ], cytochrome b [ Cytb ], and ribosomal 12S and 16S rRNA genes) and four nuclear genes (exon regions of myosin, heavy polypeptide [ Myh6 ]; patched domain‐containing protein 1 gene [ Ptchd1 ]; recombination activating gene 1 [ Rag1 ]; and recombination activating gene 2 [ Rag2 ]).…”

“…The new genus and species were coded for all the morphological data of both matrices following Mirande () and Vanegas‐Ríos (). In the data set A, the script “bloqmorph” was used to select the same species that were analyzed by Mirande () in his final analyzed data matrix under the criteria of including only those terminal taxa coded for the morphological partition and characid species (his ingroup) having molecular information for at least four markers, even when their morphological coding was missing.…”

“…Within the Stevardiinae, the presence of a hypertrophied terminal caudal‐fin squamation either present in both sexes or restricted to adult males (Menezes & Weitzman, ; Vanegas‐Ríos, ) is found in a relatively large number of genera: Acrobrycon Eigenmann & Pearson; Argopleura Eigenmann; Chrysobrycon Weitzman & Menezes; Corynopoma Gill, Diapoma Cope (in part); Gephyrocharax Eigenmann, Glandulocauda Eigenmann, Hysteronotus Eigenmann; Iotabrycon Roberts; Lophiobrycon Castro, Ribeiro, Benine & Melo, Mimagoniates Regan. Phenacobrycon Eigenmann; Planaltina Böhlke; Pseudocorynopoma Perugia; Pterobrycon Eigenmann; Ptychocharax Weitzman, Fink, Machado‐Allison & Royero; Scopaeocharax Weitzman & Fink; Trochilocharax Zarske; Tyttocharax Fowler and Xenurobrycon Myers & Miranda‐Ribeiro.…”

“…Phenacobrycon Eigenmann; Planaltina Böhlke; Pseudocorynopoma Perugia; Pterobrycon Eigenmann; Ptychocharax Weitzman, Fink, Machado‐Allison & Royero; Scopaeocharax Weitzman & Fink; Trochilocharax Zarske; Tyttocharax Fowler and Xenurobrycon Myers & Miranda‐Ribeiro. In addition to that squamation, all those genera can be partly or exclusively diagnosed or defined by other remarkable features associated with bony hooks, caudal muscles, and spur‐shaped structures (Arcila, Vari, & Menezes, ; Menezes & Weitzman, ; Vanegas‐Ríos, ; Weitzman & Fink, ; Weitzman & Menezes, ; Weitzman, Menezes, Evers, & Burns, ; Zarske, ). Most characters related to the terminal caudal‐fin squamation have played a crucial role in defining stable generic limits among the stevardiines, especially in those species with modified squamation on the lower caudal‐fin lobe (Arcila et al, ; Deprá, Graça, Pavanelli, Avelino, & Oliveira, ; Menezes, Weitzman, & Burns, ; Vanegas‐Ríos, , ; Weitzman & Fink, ; Weitzman, Fink, Machado‐Allison, & Royero, ;Weitzman & Malabarba, ; Weitzman & Thomerson, ); with Diapoma as the only exception (Thomaz et al, ; Vanegas‐Ríos, Azpelicueta, & Malabarba, ).…”

“…In addition to that squamation, all those genera can be partly or exclusively diagnosed or defined by other remarkable features associated with bony hooks, caudal muscles, and spur‐shaped structures (Arcila, Vari, & Menezes, ; Menezes & Weitzman, ; Vanegas‐Ríos, ; Weitzman & Fink, ; Weitzman & Menezes, ; Weitzman, Menezes, Evers, & Burns, ; Zarske, ). Most characters related to the terminal caudal‐fin squamation have played a crucial role in defining stable generic limits among the stevardiines, especially in those species with modified squamation on the lower caudal‐fin lobe (Arcila et al, ; Deprá, Graça, Pavanelli, Avelino, & Oliveira, ; Menezes, Weitzman, & Burns, ; Vanegas‐Ríos, , ; Weitzman & Fink, ; Weitzman, Fink, Machado‐Allison, & Royero, ;Weitzman & Malabarba, ; Weitzman & Thomerson, ); with Diapoma as the only exception (Thomaz et al, ; Vanegas‐Ríos, Azpelicueta, & Malabarba, ). However, and as found in different phylogenetic studies using morphological data, the mere presence of the hypertrophied caudal‐fin squamation does not support a monophyletic group (Ferreira, Menezes, & Quagio‐Grassioto, ; Menezes & Weitzman, ; Mirande, ; Vanegas‐Ríos, ; Weitzman et al, ).…”