Drainage rearrangements and in situ diversification of an endemic freshwater fish genus from north‐eastern Brazilian rivers

Drainage rearrangements, either headwater captures or coastal paleodrainages formed when sea level was low, are often invoked to explain connectivity and isolation among fish populations. Unravelling these events is crucial for understanding the evolutionary processes that have shaped genetic diversity differentiation in freshwater fishes, which especially relevant regions with high endemism species richness. Here, we analyse mitochondrial (cytochrome c oxidase subunit I) genomic (restriction site-associated DNA) data test putative effects of current configuration basins historical drainage rearrangements on structuring a characid (Nematocharax) endemic largely overlooked Neotropical ecoregion—the North-eastern Mata Atlantica. Bathymetric geomorphological were also used generate hypotheses two potential routes dispersal (headwater paleodrainages). We found divergence between lineages from highlands Brazilian shield lowlands occurred during Mio-Pliocene (i.e., Nematocharax varii venustus), followed by within N. venustus lowland Pleistocene. The general distribution variation seems reflect basins, suggesting long-term isolation, but subset inferred facilitated movement catchments, supported both DNA data. Our results suggest Atlantica river had their own independent histories, except some past temporary connections allowed multiple colonisation as seen Contas Cachoeira systems. Estimating where may fundamental understand role different species.