Ecological niche modelling and genetic analyses reveal lack of geographic differentiation of Leptolobium dasycarpum (Leguminosae, Papilionoideae) across the Brazilian savannah

Abstract

Trees from Brazilian savannah (Cerrado), especially species of the family Leguminosae, generally show genetic discontinuity among their populations. This leads to the formation of geographically delimited groups. This study assesses the effects of historical climatic changes during the Quaternary glaciations on the demography, diversification and spatial distribution of Leptolobium dasycarpum, a useful tree species of the Cerrado, using phylogeography and spatial distribution modelling. We sampled freshly collected and herborized individuals throughout L. dasycarpum’s distribution and sequenced two plastid intergenic spacers (133 plants) and the ITS region from the nuclear ribosomal DNA (124 plants). The current study’s framework incorporated statistical phylogeography, coalescent analyses and ecological niche modelling. The species presented significant differentiation among populations, with no geographically differentiated groups along the Cerrado and no signs of recent demographic changes. The species also experienced a moderate reduction of its suitable niche distribution during the Last Glacial Maximum. Moreover, the data suggested that the ancestral distribution area of L. dasycarpum was the central Cerrado and that colonization of adjacent areas occurred only recently. The results suggested that the central region of the Cerrado is the centre of L. dasycarpum lineage diversification and there are no significant barriers to gene flow among populations from the different regions of Cerrado. Historical climate changes did not impact the demographic history of L. dasycarpum probably due to the demographic stability throughout the Quaternary allied to the life history traces of this species.