Species delimitation and historical biogeography of Sturisoma Swainson, 1838 (Loricariidae: Loricariinae): Hidden diversity along the Amazon River

In the present study, we used DNA sequences from three mitochondrial (COI, Cytb, and nd2) and one nuclear (RAG2) marker, to perform species delimitation analyses (ABGD, GMYC, BPP, and bPTP) within Sturisoma to test the validity of currently recognized and potential new species for the genus. Additionally, a historical biogeographic analysis was carried out to test the age and centers of origin for species of the genus. Results found here indicate a high degree of genetic divergence with overlapping morphological characteristics suggesting a greater diversity than previously proposed for the genus. All valid species currently included in Sturisoma were confirmed here, and one potentially undescribed species was recovered. Based on genetic distances, geographical patterns and historical biogeography, the diversification of the group could be related to dispersal events from Western to Eastern Amazonia resulting in sympatric species that are highly divergent genetically but conservative morphologically. The lower (eastern) Amazonas and the Orinoco River basins were identified as the main centers of origin for the genus, with an approximate age of origin of 13 Mya, during the Miocene. The diversity of the genus is likely to be even higher because the Amazon River is a hotspot of hidden biodiversity.