Phylogeography and ecological niche modelling, coupled with the fossil pollen record, unravel the demographic history of a Neotropical swamp palm through the Quaternary

AimThe recovery of demographic history through phylogeographical analysis is critical for understanding microevolutionary processes and the spatial/temporal context of lineage divergence. Palaeodistribution modelling and the fossil record might provide the spatial context for statistical phylogeographical analyses, allowing the generation of independent palaeoscenarios of demographic history that can be tested using coalescent models. In this study we generated independent demographic scenarios to examine geographical barriers to gene flow in a Neotropical swamp palm, Mauritia flexuosa, and assessed how climatic changes during the Pleistocene influenced its geographical distribution and genetic diversity. LocationNeotropical wetlands. MethodsWe sampled 257 adult individuals of M. flexuosa from 26 localities in the Amazon, Araguaia/Tocantins, Paraguai, Parana and SAo Francisco basins. The analyses were based on statistical phylogeography, ecological niche modelling and the fossil pollen record. The genetic data were based on polymorphisms in three chloroplast non-coding regions. ResultsMauritia flexuosa presented low genetic diversity but significant genetic differentiation among populations from different river basins. The ecological niche modelling and demographic simulations showed that the pattern of observed genetic diversity for M. flexuosa probably reflects range retraction during the Last Glacial Maximum, leading to multiple refugia. In support of this, the fossil pollen record suggests that multiple refugia were present in Brazilian savannas, where M. flexuosa often disappeared during cold and dry periods across the last glacial cycle, returning during the wet phases. The periodic dryness in this region was driven by the latitudinal displacement of the Intertropical Convergence Zone (ITCZ) across glacial/interglacial periods, which possibly affected the distributional dynamics of M. flexuosa during the Pleistocene epoch. Main conclusionsOur results provide evidence that climate changes during the last glacial cycle were important determinants of the geographical distribution and demographic history of M. flexuosa across the late Quaternary period. In addition to the geographical barriers imposed by river basins, these factors have shaped genetic differentiation, as currently observed among lineages.