Molecular and morphological evidence revalidates Acrobrycon tarijae (Characiformes, Characidae) and shows hidden diversity

Abstract

We conducted a revision of the Neotropical genus Acrobrycon. A previous study synonymized the species, A. ipanquianus, distributed from the western portion of the Amazon River to the north-western region of the La Plata River Basin, and A. tarijae, with type locality in the Lipeo River in Bolivia. We revisited this result by collecting new morphometric, meristic, and genetic data (COI mitochondrial gene) for 24 individuals distributed along La Plata River Basin in Argentina, and discussed our results in the context of multiple biogeographic processes of isolation in that basin. Our results revealed a more complex history of diversification and geographic distribution across Acrobrycon species than previously suspected, probably associated with multiple biogeographic processes of isolation in La Plata River Basin. We present new evidence that led us to reconsider the validity of A. tarijae, which is distinguishable from A. ipanquianus by the number of vertebrae (37–39 vs. 41–42) and pleural ribs (12–13 vs. 14). These results were also supported by our molecular analyses that revealed a genetic divergence >4% between A. ipanquianus and A. tarijae. We also identified two main genetic clusters within A. tarijae: the first cluster consisted of specimens from the Bermejo, Pilcomayo, Itiyuro and Juramento river basins (northern Argentina); and the second cluster included specimens from the southernmost basins, such as the Salí River in Tucumán, Cuarto River in the province of Cordoba and the Quinto River in the province of San Luis. Our results suggest that the genetic structure observed in A. tarijae is the result of the type of drainage (endorheic vs. exorheic) and geographical distance.

Revision of Bryconamericus (Characiformes, Characidae) from Pacific coastal and Amazon River drainages with descriptions of three new species

“…Upon comparison of the data from the types of B. alfredae and A. ipanquianus (Table6;Arcila et al 2013, table 1, and see comparative material examined), some differences were noted in body depth, position of the dorsal fin relative to the anal-fin origin, and in the length and depth of the caudal peduncle. We believe that most of these differences are in part due to the poor state of conservation of the types of B. alfredae (Fig.11); Moreover,Briñoccoli et al (2022), reconsider the validity of A. tarijae, which is distinguishable from A. ipanquianus by the number of vertebrae (37-39 vs. 41-42) and pleural ribs (12-13 vs. 14). So we consider Bryconamericus alfredae to be a junior synonym of A. ipanquianus Weitzman et al (2005).…”

¿Sabemos lo que estamos conservando? Peces del Parque Nacional Aconquija, Tucumán, Noroeste de Argentina

“…CI FML 7914, 8 ex, 27° 21' 23.8" S, 65° 48' 33.3"W Cochuna River. CI FML 7917, 12 ex, 27°21'23.8" Number of perforated scales of the lateral line: 51-60; number of horizontal-scale rows around the caudal peduncle: 19-21; lower number of vertebrae (37-39); and pleural ribs: 12-13 pairs; number of branched anal-fin rays: 23-27; presence of a glandular pocket at the base of the lower lobe of the caudal fin in males; orange adipose fin(Briñoccoli et al, 2022).…”