Chaetostoma branickii Steindachner 1881

Chaetostoma branickii Steindachner 1881 Figs 4, 5 Chaetostoma breve Regan 1904 [synonym] Diagnosis and description. As for Chaetostoma breve in Lujan et al. (2015 a). Comments. Regan (1904) based the description of Chaetostoma breve on specimens from the Zamora River in south-eastern Ecuador. Lujan et al. (2015 a) re-described Chaetostoma breve based on specimens from throughout most of the species’ range, from the Napo River in the north (although the species is also now known from more northern Caqueta River headwaters in Colombia; ROM 107831, 107845) to the Marañon River in the south. Lujan et al. (2015 a) also generated a multi-locus molecular phylogenetic hypothesis spanning over 24 valid and undescribed species, with Chaetostoma breve represented by samples from the Napo, Pastaza, Marañon, Santiago and Huallaga River Basins. Bayesian and Maximum Likelihood analyses found uniformly strong support for monophyly of the entire Chaetostoma breve clade (Bayesian posterior probability: 1.00, Maximum Likelihood bootstrap: 100). Chaetostoma branickii was described by Steindachner (1881), based on specimens from the Chota River near Cajamarca in northern Peru. That portion of the Marañon River Basin was poorly sampled at the time of Lujan et al. (2015 c), thus few specimens and no tissues from that specific region were available, making it reasonable to assume that a distinct, endemic species might exist there. Moreover, the syntypes of Chaetostoma branickii were in Vienna and not directly accessible to the authors. Lujan et al. (2015 c) concluded that Chaetostoma branickii might be more closely allied with Chaetostoma taczanowskii, which was described by Steindachner (1881), based on specimens from the Huallaga River drainage to the south. To further investigate the validity of Chaetostoma branickii, Lujan and colleagues sampled the upper middle Marañon River in 2018, collecting over 540 fresh specimens and 60 tissues of Chaetostoma. This new material allowed a more detailed comparison of fresh, nearly topotypic specimens with the specimens on which Lujan et al. (2015 a) based their re-description of Chaetostoma breve and type images of Chaetostoma branickii (Figs 4, 5). Based on this comparison, it has become clear that these are the same species and that Chaetostoma branickii should thus be recognised as the senior synonym of Chaetostoma breve. Chaetostoma taczanowskii Steindachner 1882 is another taxonomically ambiguous species from northern Peru, described from the Huallaga River Basin, a southern tributary of the Marañon. Type images of this species suggest that it is also closely related to Chaetostoma branickii, if not another junior synonym, but a robust evaluation of the status of this species must await availability of fresh topotypic specimens and tissues.