Taxonomy of Moenkhausia australis Eigenmann, 1908 (Characiformes, Characidae) with a discussion on its phylogenetic relationships

The
species Moenkhausia australis was
described based on two specimens from arroyos Trementina and Chagalalina, Rio
Paraguai basin, Paraguay. Its taxonomic history is complex and for many years the
species was considered a synonym of Moenkhausia
sanctaefilomenae. Moenkhausia
australis shares a reticulated color pattern with the Moenkhausia oligolepis/M.
sanctaefilomenae complex, being more
similar within the species included in the complex to M. oligolepis, M. sanctaefilomenae,
and M. forestii, with which it shares a prepelvic region laterally
compressed, a feature also observed in Bario
steindachneri. The laterally compressed prepelvic region is inferred to be putatively
synapomorphic for the subgroup herein denominated as Moenkhausia oligolepis group. Our results, based on both molecular
and morphological data, support the validity of Moenkhausia australis, which can be readily distinguished from the
other members of the group by possessing complete lateral line, 23–27 scales in the lateral line,
and five scales series above and below the lateral line. Our analysis also
indicates three genetic structured populations of M. australis, from Rio
Paraguai, upper Rio Paraná, and Rio Madeira basins. Since they are not
diagnosable by morphological characters, we conservatively maintain all these
three genetic lineages as a single species.