Abstract
This study presents the description of a new genus of the catfish subfamily Neoplecostominae from the Tocantins River basin. It can be distinguished from other neoplecostomine genera by the presence of (1) three hypertrophied bicuspid odontodes on the lateral portion of the body (character apparently present in mature males); (2) a large area without odontodes around the snout; (3) a post-dorsal ridge on the caudal peduncle; (4) a straight tooth series in the dentary and premaxillary rows; (5) the absence of abdominal plates; (6) a conspicuous series of enlarged papillae just posterior to the dentary teeth; and (7) caudal peduncle ellipsoid in cross section. We used maximum likelihood and Bayesian methods to estimate a time-calibrated tree with the published data on 116 loricariid species using one nuclear and three mitochondrial genes, and we used parametric biogeographic analyses (DEC and DECj models) to estimate ancestral geographic ranges and to infer the colonization routes of the new genus and the other neoplecostomines in the Tocantins River and the hydrographic systems of southeastern Brazil. Our phylogenetic results indicate that the new genus and species is a sister taxon of all the other members of the Neoplecostominae, originating during the Eocene at 47.5 Mya (32.7–64.5 Mya 95% HPD). The present distribution of the new genus and other neoplecostomines may be the result of a historical connection between the drainage basins of the Paraguay and Paraná rivers and the Amazon basin, mainly through headwater captures.
Highlights
The Loricariidae, an endemic Neotropical family of freshwater fish, is the largest group of catfish, with about 900 valid species (Eschmeyer and Fong 2015)
Microplecostomus forestii sp. n. differs from species of the genera Isbrueckerichthys, Neoplecostomus and Pseudotocinclus by (4) the absence of abdominal plates, Fig. 1; from Kronichthys by having (5) the tooth series in dentary and premaxillary rows straight; from Neoplecostomus by (6) the absence of a conspicuous series of enlarged papillae just posterior to the dentary teeth; and from Pseudotocinclus by having (7) the caudal peduncle ellipsoid in cross section
The results of our molecular analyses indicated that Microplecostomus forestii sp. n. is the sister-group of all the other members of the Neoplecostominae (Fig. 8), with strong statistical support
Summary
The Loricariidae, an endemic Neotropical family of freshwater fish, is the largest group of catfish, with about 900 valid species (Eschmeyer and Fong 2015). Chiachio et al 2008; Roxo et al 2012a, 2014) concluded that the considerable diversity of this subfamily can be accounted for primarily by the geomorphological processes (i.e. tectonics and erosion) that have shaped the South American continent over the past 100 Mya, influencing fish distribution and speciation patterns (Ribeiro 2006; Albert and Reis 2011) In this context, one of the principal processes is river capture ( known as stream capture or headwater capture), an important landscape-level mechanism that can isolate lineages and promote diversification (Waters et al 2006; Winemiller et al 2008; Albert and Crampton 2010) by changing the connectivity of adjacent river basins (Smith 1981; Hocutt and Wiley 1986; Mayden 1988; Lundberg et al 1998). The consequences of this process for the local fauna can be profound, changing watershed boundaries and allowing previously isolated species to disperse and colonize new environments (Grant et al 2007; Muneepeerakul et al 2008; Bertuzzo et al 2009)
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