Monday, January 9, 2017

[Ichthyology • 2017] Multilocus Molecular Phylogeny of the Ornamental Wood-eating Catfishes (Siluriformes, Loricariidae, Panaqolus and Panaque) reveals Undescribed Diversity and Parapatric Clades


Fig. 1. Voucher specimens examined in this study, from the new subgenus Panafilus (lyretail clown plecos):
(1) Pf. albivermis, (2) Pf. albomaculatus, (3) Pf. nocturnus, (4) Pf. n. sp. Huallaga L329, (5) Pf. n. sp. Huallaga L351, (6) Pf. n. sp. Ucayali L425, (7) Pf. n. sp. Moa L453, (8) Pf. n. sp. Napo L466, (9) Pf. nix, (10) Pf. n. sp. Madeira;
 new subgenus Panaqoco (Orinoco clown plecos): (11) Pc. maccus, (12) Pc. n. sp. Tomo L465, (13) Pc. n. sp. Orinoco L448;
new subgenus Panaqolus (the tiger clown plecos): (14) Pq. changae, (15) Pq. gnomus, (16) Pq. purusiensis, (17) Pq. n. sp. Curua Una, (18) Pq. n. sp. Tocantins L002, (19) Pq. n.sp. Negro L169, (20) Pq. n. sp. Ucayali L206, (21) Pq. n. sp. Branco L306, (22) Pq. n. sp. Amazon L397, (23) Pq. tankei, (24) Pq. n. sp. Itaya L459;
and new genus Pseudoqolus: (25) Ps. koko.

Highlights
• Respective genera Panaqolus (exclusive of putative congener ‘Panaqolus’ koko) and Panaque are strongly monophyletic. 
• Within Panaqolus s.s., species are distributed across three strongly monophyletic clades.
• New subgenera are erected for each of the three subclades within Panaqolus.
• A new genus is erected for the enigmatic species ‘Panaqolus’ koko.
• Western tributaries of the Amazon Basin are an epicenter of wood-eating catfish diversity.

Abstract
Approximately two-dozen species in three genera of the Neotropical suckermouth armored catfish family Loricariidae are the only described fishes known to specialize on diets consisting largely of wood. We conducted a molecular phylogenetic analysis of 10 described species and 14 undescribed species or morphotypes assigned to the wood-eating catfish genus Panaqolus, and four described species and three undescribed species or morphotypes assigned to the distantly related wood-eating catfish genus Panaque. Our analyses included individuals and species from both genera that are broadly distributed throughout tropical South America east of the Andes Mountains and 13 additional genera hypothesized to have also descended from the most recent common ancestor of Panaqolus and Panaque. Bayesian and maximum likelihood analyses of two mitochondrial and three nuclear loci totaling 4293 bp confirmed respective monophyly of Panaqolus, exclusive of the putative congener ‘Panaqolus’ koko, and Panaque. Members of Panaqolus sensu stricto were distributed across three strongly monophyletic clades: a clade of 10 generally darkly colored, lyretail species distributed across western headwaters of the Amazon Basin, a clade of three irregularly and narrowly banded species from the western Orinoco Basin, and a clade of 11 generally brown, broadly banded species that are widely distributed throughout the Amazon Basin. We erect new subgenera for each of these clades and a new genus for the morphologically, biogeographically and ecologically distinct species ‘Panaqolus’ koko. Our finding that perhaps half of the species-level diversity in the widespread genus Panaqolus remains undescribed illustrates the extent to which total taxonomic diversity of small and philopatric, yet apparently widely distributed, Amazonian fishes may remain underestimated. Ranges for two Panaqolus subgenera and the genus Panaque overlap with the wood-eating genus Cochliodon in central Andean tributaries of the upper Amazon Basin, which appear to be a global epicenter of wood-eating catfish diversity.

Keywords: Neotropics; undescribed species; L-numbers; biogeography; western Amazon; introgression




Conclusions
Our finding that approximately half of the species-level diversity in the widespread genus Panaqolus may remain undescribed is illustrative of the extent to which total taxonomic diversity of even commercially exploited Amazonian fish lineages may remain underestimated by current taxonomies. Our erection of strongly monophyletic subgenera for the species-rich genus Panaqolus should help to facilitate both the conservation and taxonomic description of species by making at least the major clades easier to identify and by restricting the number of congeners that future taxonomists would have to examine to adequately diagnosis new Panaqolus species. Moreover, our strong phylogenetic support for large-scale biogeographical influence on the diversification of Panaqolus helps to justify and spatially delimit studies by regional researchers with regular access only to collections representing regional diversity.

It is clear from the biogeographical patterns observed in both Panaqolus and Panaque, as well as the Cochliodon group examined elsewhere (e.g., Armbruster, 2003), that Andean affluents of the southwestern Amazon Basin are an epicenter of wood-eating fish diversity, with some drainages having up to five different sympatric but unrelated species of wood-eating catfish coexisting on the same pieces of submerged wood. See Lujan et al. (2011) for a detailed study of trophic resource partitioning in one such diverse assemblage.


Nathan K. Lujan, Christian A. Cramer, Raphael Covain, Sonia Fisch-Muller and Hernán López-Fernández. 2017. Multilocus Molecular Phylogeny of the Ornamental Wood-eating Catfishes (Siluriformes, Loricariidae, Panaqolus and Panaque) reveals Undescribed Diversity and Parapatric Clades. Molecular Phylogenetics and Evolution. In Press.  DOI: 10.1016/j.ympev.2016.12.040
  

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