Species delimitation in Neotropical fishes of Mesonauta Günther 1862 (Cichliformes: Cichlidae)

From Neotropical cichlids, Mesonauta accomplishes six described species, but although Mesonauta have few described species, putative new species are referred to this genus. Considering that understanding the boundaries of each species could help in phylogenetic context, here, we use a DNA-barcode technique to (1) delimit species within Mesonauta, (2) to test the M. insignis species complex, and (3) discuss the Mesonauta species distribution. The Maximum likelihood tree used under the three delimitation methods does not corroborate the six species previously described and the ten morphotypes. According to the mitochondrial data used herein, despite some differences in coloration pattern, the genus is composed by the following: (1) Mesonauta mirificus, widely distributed from several tributaries from the Amazon River basin, Suriname, Takutu, Branco, Oiapoque, Tapajós, Moa, Negro and Xingu Rivers (including M. guyanae); Mesonauta festivus, composed by two species: (2) M. festivus from Guaporé River basin and (3) Mesonauta sp. “Pantanal” from Paraguay River basin; (4) M. acora, distributed in the Tocantins-Araguaia and Xingu River basins; (5) Mesonauta sp. “Amapá”, from Amapá Grande River basin and Jeju River; and (6) M. insignis, from upper Negro, Colombian, and Venezuelan Orinoco Rivers. There were no molecular differences between Mesonauta egregius described from the Orinoco River basin and M. insignis, or between M. mirificus and M. guyanae from Amazon/Suriname River basin. Further, PCA analysis and color pattern are insufficient to differentiate M. festivus from Mesonauta sp. “Pantanal”. These findings offer a unique perspective on cichlid diversity and provide the basis for future research focusing on the widely distributed Mesonauta mirificus.