The impact of Quaternary Amazonian river dynamics on patterns and process of diversification in uakari monkeys (genusCacajao)

Abstract

ABSTRACTAimWestern Amazonia is a region that underwent several landscape changes during the Quaternary. While Riverine Barrier Hypothesis is traditionally used to explain the influence of rivers on speciation, processes such as river rearrangements have been overlooked to explain the geographic distribution and evolutionary history of the Amazonia biota. Here we test how river rearrangements in western Amazonia influenced the evolutionary history of uakari monkeys, a primate group most associated with seasonally flooded forests in western Amazonia.LocationWestern AmazoniaTaxonThe uakari monkey (genusCacajao)MethodsWe performed a continuous phylogeographic analysis using 77 cytochromebsequences and used digital elevation models to identify the role of landscape and riverscape characteristics in the geographic distribution ofCacajao. Finally, we used genome-wide SNPs variation (ddRADseq) to investigate population structure, gene flow and demographic history in threeCacajaospecies that were impacted by river rearrangements.ResultsOur continuous phylogeographical reconstruction points that the ancestralCacajaolineage occupied the flooded forests of the Solimões River at ∼1.7 Mya, and descendant lineages dispersed throughout western Amazonia more recently. We identified gene flow among both black and bald-headed uakari populations, even across rivers considered barriers (e.g., the Negro River). Landscape analysis showed that river rearrangements influenced the geographic distribution and population structure inCacajao. The demographic analysis indicates thatC. calvus, C. amuna, andC. rubicunduswent through a population decline in the last 70 Kya and have a low effective population size.Main conclusionOur results support that the river rearrangements have shaped the geographic distribution and divergence of recently divergedCacajaolineages. Landscape and riverscape changes, along with retractions of the flooded forests, isolated someCacajaopopulations in floodplain areas. Our study also suggests that these events led to the recent population decline in species with a restricted geographic distribution.