https://onlinelibrary.wiley.com/doi/abs ... /jfb.14467
Abstract
n. sp. was discovered during a multitaxonomic scientific expedition to the remote Amazon Terra do Meio region in tributaries to the rio Xingu basin, Pará, Brazil. The new species can be promptly distinguished from its congeners by the following combination of features: (I) absence of the first dorsal‐fin element; (II) parieto‐supraoccipital fontanel located medially on bone; (III) absence of a longitudinal dark brown or black stripe along flank midline; (IV) ventral surface of trunk covered by clearly smaller, irregular and/or roundish platelets; (V) inner laminar expansion of infraorbital 1 well developed; (VI) relatively wide frontal bone, with width equal to half of entire length; (VII) absence of a thick, longitudinal conspicuous dark brown stripe along dorsal portion of flank; and (VIII) poorly developed serrations on posterior margin of the pectoral‐fin spine. Besides morphological evidence, the molecular analyses indicated significant differences between the new species and its congeners, with A. albater and A. raimundi as its closest species, showing 6.53% of genetic differentiation in both cases. The intraspecific molecular data revealed gene flow (FST = 0.21641 for the COI marker, and FST = 0.53213 for the Control Region) between specimens from upstream and downstream a 30‐meters height waterfall at the type‐locality, which therefore represent a single population (P = 0.001 for COI, and P = 0.007 for the Control Region). Furthermore, it was possible to observe a unidirectional gene flow pattern, with genetic diversity increasing in the downstream direction.
