Population dynamics and evolutionary history of the genus Sakesphorus (Aves: Thamnophilidae) in the Amazonian...

The genus Sakesphorus (Aves: Thamnophilidae) includes two species that are floodplain specialists within Amazonia. While S. luctuosus occupies floodplains of southeastern Amazonia and extends south along riparian habitats in central Brazil, S. canadensis occupies northern Amazonian floodplains and extends to other habitat types in northern South America, including mangroves, deciduous forests, and savannas. We reconstruct the historical diversification of the genus to investigate the landscape history of the Amazonian floodplains and their relationships with adjacent environments. We used reduced representation genomic data obtained with Ultra conserved Elements (UCE) probes and mtDNA from 26 S. canadensis and 30 S. luctuosus individuals. The phylogenetic analyses recovered each species as a well-supported clade. The split between the two species dates to 2.67 Ma (CI: 1.66-3.91), with a crown age of 620 Kya (CI: 0.37-0.91) for S. canadensis and 330 (CI: 0.2-0.49) Kya for S. luctuosus. Sakesphorus canadensis comprises three populations with low migration rates between them. Demographic expansion was unequivocal only for the Branco River population (S. c. fumosus), suggesting an association with the evolution of the Branco River drainage. Pleistocene diversification of the genus corroborates the dynamism of the Amazonian fluvial system during this period, affecting connectivity along Amazonian floodplains and driving population differentiation. Connectivity with adjacent biomes through riparian corridors was important for the evolution of Amazonian floodplain biodiversity and should be protected.