Abstract
A new species of Aphyocharax is described from the Maracaçumé river basin, eastern Amazon, based on morphological and molecular data. The new species differs from all its congeners, mainly by possessing the upper caudal-fin lobe longer than the lower one in mature males, and other characters related to teeth counts, colour pattern, and body depth at dorsal-fin origin. In addition, the new species is corroborated by a haplotype phylogenetic analyses based on the Cytochrome B (Cytb) mitochondrial gene, where its haplotypes are grouped into an exclusive lineage, supported by maximum posterior probability value, a species delimitation method termed the Wiens and Penkrot analysis (WP).
Highlights
The Neotropical fish genus Aphyocharax Günther, 1868 is distributed along the river basins of the Orinoco, Amazon, and La Plata systems, as well as in the river systems drainaing the Guiana Shield (Géry 1977; Taphorn and Thomerson 1991; Tagliacollo et al 2012; Brito et al 2018; Fricke et al 2019), with highest diversity in the Amazon basin (Fricke et al 2019)
Three morphological synapomorphies have been proposed for Aphyocharax: (1) narrow trigeminofacialis foramen like a cleft with sphenotic almost excluded from its margin; (2) dorsal projection of maxilla overlaping the second infraorbital; and (3) dorsal margin of third postcleithrum not projecting dorsally to posterior region of scapula (Mirande 2010; Tagliacollo et al 2012)
Few studies focused on the intrageneric phylogenetic relationships within Aphyocharax (e.g Tagliacollo et al 2012), and its diversity is probably underestimated, with at least four undescribed species (Souza-Lima 2007) and several populations or species waiting for a taxonomic revision (Lima et al 2013; Ohara et al 2017; Brito et al 2018)
Summary
The Neotropical fish genus Aphyocharax Günther, 1868 is distributed along the river basins of the Orinoco, Amazon, and La Plata systems, as well as in the river systems drainaing the Guiana Shield (Géry 1977; Taphorn and Thomerson 1991; Tagliacollo et al 2012; Brito et al 2018; Fricke et al 2019), with highest diversity in the Amazon basin (Fricke et al 2019). Tagliacollo et al (2012) included seven valid species of Aphyocharax in their phylogenetics analysis, and provided a hypothesis of interspecific relationships based on both molecular and morphological datasets. Their parsimony-based total evidence analysis (TE) indicates that Aphyocharax and Prionobrama Fowler, 1913 form a clade supported by three morphological synapomorphies: (1) interrupted lateral line with a single perforated scale on the posterior region of caudal peduncle; (2) absence or reduction of the fourth infraorbital bone canal; and (3) presence of a single large cusp on anterior maxillary teeth. Several other morphological features have been commonly used to characterize Aphyocharax species, such as the red caudal-fin colouration, moderately elongated body, single series of tricuspid teeth on the premaxilla and mandible, and maxilla with teeth on up to two-thirds of its ventral margin (Taphorn and Thomerson 1991; Willink et al 2003; Tagliacollo et al 2012; Brito et al 2018)
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