Patterns of genetic differentiation in the Gymnogeophagus gymnogenys species complex, a neotropical cichlid from South American basins

Abstract

The neotropical cichlid genus Gymnogeophagus is distributed in the Rio de la Plata basin and in Dos Patos and Merin coastal lagoons on the border between Uruguay and southern Brazil. A phylogeographic approach based on mitochondrial cytochrome b analysis was performed to assess the patterns and processes of differentiation in this taxon. Gymnogeophagus gymnogenys showed high haplotype diversity (H = 0.992) and corrected mtDNA genetic distances ranged from 0 to 5.3%. Our analyses yielded robust support for the existence of four monophyletic groups within G. gymnogenys from the analyzed basins. No correlation between the aforementioned clades and geographic structure was found, since individuals belonging to different phylogenetic clades inhabit the same locality. The phylogeographic approach presented here showed that these four phylogroups (1, 2, 3 and 4) were sister groups. Our present findings would corroborate that G. gymnogenys could be integrated by different phylogenetic lineages, showing an explosive differentiation pattern and confirming the hypothesis that this taxon constitutes a species complex.