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• Genetic data and species distribution models reveal spatio-temporal dynamics of dry forest. • Climatic changes in the quaternary cannot be regarded as the main cause for the molecular divergence amongst the haplotypes of Anadenanthera colubrina var. cebil. • The distribution of Anadenanthera colubrina var. cebil was widespread and fragmented in the Pleistocene in South America even before the LGM. • Fossil data show the occurrence of Anadenanthera colubrina var. cebil in northern Argentina since the Miocene. Neotropical seasonally dry forest (dry forest) is a fragmented biome that occurs in regions with pronounced seasonal rainfall. There are several hypotheses about the evolution of the distribution of these forests concerning the influence of climatic changes during the Quaternary. Anadenanthera colubrina var. cebil is a native tree that is considered the most paradigmatic and ecologically specialized key species of dry forest. The present work aims to test whether the current disjunct distribution of A. colubrina var. cebil is a remnant of a formerly widespread range during the cold and dry phases of the Last Glacial Maximum (LGM). Here, we take an approach that combines chloroplast DNA, palaeodistribution modelling and fossil evidence to understand the spatial and temporal dynamics of the distribution of Anadenanthera colubrina var. cebil. Seven haplotypes were detected in the two non-coding regions of cpDNA analysed and their divergence was dated to the Neogene. Maps of climatic suitability for A. colubrina var. cebil throughout South America showed that the potential distribution of the species was extensive and fragmented from the lower Pleistocene to modern times. Data from the fossil record confirm the occurrence of A. colubrina var. cebil at the southern limit of the dry forest distribution in historical times before the Quaternary. We found that climate change during the Pleistocene cannot be considered the main cause of molecular divergence of A. colubrina var. cebil haplotypes. We also found that A. colubrina var. cebil already had a widespread and fragmented distribution in South America during the Pleistocene, and that A. colubrina var. cebil was already present in northern Argentina in pre-Pleistocene. [ABSTRACT FROM AUTHOR]

The presence of Anadenanthera colubrina var. colubrina for the Argentinean flora is confirmed. This variety is distinguished by three morphological characters: structure of the inflorescence, fruit characteristics and venation type of the folioles, being the latter very useful when studying vegetative material. The variety colubrina inhabits the same areas as var. cebil. A distribution map, illustrations and a key to identify the varieties are presented, and lectotypes are designated for Piptadenia macrocarpa and Niopa. [ABSTRACT FROM AUTHOR]