Abstract
Abstract We propose a revised classification of Doradidae based on phylogenetic analyses of sequence data for one nuclear (rag1) and two mitochondrial (co1, 16s) genes, and corroborated by caudal-fin morphology. The molecular dataset comprises 174 doradid specimens representing all 31 valid genera, 83 of the 96 valid extant species and 17 species-level taxa that remain undescribed or nominally unassigned. Parsimony and Bayesian analyses of molecular data support six major lineages of doradids assigned here to three nominal subfamilies (Astrodoradinae, Doradinae, Wertheimerinae) and three new ones (Acanthodoradinae, Agamyxinae, Rhinodoradinae). The maximum parsimony topology of Doradidae was sensitive to ingroup density and outgroup age. With the exceptions of Astrodoradinae and Doradinae, each subfamily is diagnosed by caudal-fin characteristics. The highest degree of fusion among skeletal elements supporting the caudal fin is observed in Acanthodoradinae and Aspredinidae, lineages that are sister to the remaining doradids and aspredinoids (i.e., Auchenipteridae + Doradidae), respectively. Fusion among caudal-fin elements tends to be higher in taxa with rounded, truncate or emarginate tails and such taxa typically occupy shallow, lentic habitats with ample structure. Caudal-fin elements are more separated in taxa with moderately to deeply forked tails that occupy lotic habitats in medium to large river channels.
Highlights
Thorny catfishes (Siluriformes: Doradidae) form a monophyletic group of about 96 valid extant and one fossil species endemic to freshwaters of South America on both sides of the Andes Mountains
180 of the 218 specimens were represented by complete molecular data
Under Maximum Parsimony (MP), the rag1 dataset consisted of 1861 total and 716 parsimony-informative base pairs for 196 specimens, the 16s dataset consisted of 583 total and 188 parsimony-informative base pairs for 211 specimens, and the co1 dataset consisted of 593 total and 246 parsimony-informative base pairs for 209 specimens
Summary
Thorny catfishes (Siluriformes: Doradidae) form a monophyletic group of about 96 valid extant and one fossil species endemic to freshwaters of South America on both sides of the Andes Mountains. Most doradids are distinguished from other catfishes by having a conspicuous midlateral row of bony scutes, each one with a central, caudally directed thorn (Fig. 1). The infranuchal scute is exceptionally composed of both an expanded tubule and an ossified ligament that runs between the nuchal region of the cranium and the rib supported by the sixth vertebra, which is the first long-formed rib. The infranuchal scute represents an unambiguous synapomorphy for Doradidae (Birindelli, 2014). Another synapomorphy for doradids is the presence of Sörensen’s ligament (Fig. 2), an unossified ligament between the anterolateral rim of the Müllerian disk and an ossified tubule or scute in the tympanic region (Birindelli, 2014)
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