Phylogeography of Oligosarcus acutirostres

What is it about?

The Northeastern Mata Atlântica freshwater ecoregion (NMAF) is recognized for the high degree of endemism of its ichthyofauna, whose evolutionary and biogeographic histories are still poorly understood. Oligosarcus acutirostris is a freshwater fish species endemic to the NMAF, which is distributed in coastal rivers and streams draining Bahia, Espírito Santo, and part of Minas Gerais states in eastern Brazil. Its widespread distribution in currently isolated river basins along the NMAF prompted this study, which aimed to understand what scenarios would be involved in determining its current distribution pattern, and to contribute to a better understanding of the biogeographic history of the NMAF. For this, mitochondrial and nuclear DNA sequences were analyzed based on samples from different localities along the species distribution, including its type locality. Overall, phylogeographic analyses indicate a strong genetic structure within the species evidenced mainly by the non-sharing of haplotypes between most of the basins analyzed. According to the AMOVA results, the current distribution of haplotypes is better explained by the Pleistocene coastal paleodrainages. The results are also used to test and complement a biogeographic hypothesis previously proposed for the drainages of the NMAF.

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Photo by Sangharsh Lohakare on Unsplash

Photo by Sangharsh Lohakare on Unsplash

Why is it important?

The study of the Northeastern Mata Atlântica freshwater ecoregion (NMAF) and its endemic fish species, such as Oligosarcus acutirostris, is important for several reasons. Conservation: Understanding the genetic structure and distribution patterns of species within the NMAF is crucial for conservation efforts. Endemic species are often more vulnerable to habitat destruction and fragmentation, and identifying distinct genetic populations can help prioritize conservation actions and protect their unique evolutionary lineages. Evolutionary and Biogeographic History: The poorly understood evolutionary and biogeographic histories of the ichthyofauna in the NMAF can be better elucidated through studies like this one. By analyzing DNA sequences from different localities and basins, researchers can reconstruct the species' evolutionary relationships and gain insights into their historical colonization and dispersal patterns. Biogeographic Hypotheses: The study aims to test and complement a biogeographic hypothesis previously proposed for the NMAF drainages. By analyzing the genetic data, researchers can assess the validity of this hypothesis and potentially refine our understanding of the historical processes that shaped the region's biodiversity. Pleistocene Coastal Paleodrainages: The results of the study indicate that the current distribution of haplotypes in Oligosarcus acutirostris can be better explained by Pleistocene coastal paleodrainages. This finding highlights the significance of historical geological events in shaping the present-day distribution patterns of species and provides valuable information for biogeographic reconstructions. Overall, this research contributes to a better understanding of the NMAF's biogeography, helps inform conservation strategies, and provides insights into the evolutionary processes that have shaped the unique ichthyofauna of this region.

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