CONICET | Buscador de Institutos y Recursos Humanos

Arachis correntina and A.villosa are perennial diploid species (2n=2x=20). The former is found in the Northeast Argentina and East of Paraguay River near Asunción (Paraguay), while the latter growths in a disjunct area along Uruguay River, from 29ºS to the North bank of La Plata River. Both taxa are morphologically similar and they have been considered as only one species. They show the most southeast distribution of the section and most of their populations are associated to watercourses. Arachis duranensis is also a diploid species and inhabits the most Southwest distribution of the section. However, this species is not currently found associated to water courses that may explain the present distribution by hydrochory. In order to understand the colonizing pathways of these species and to shed light on the evolutionary history of the section in its southern limits we analyzed the haplotypic variability in the whole range of distribution of these species and include representative populñations of all the species of the section. For this purpose, a Neighbour-Joining tree was constructed from two cpDNA regions (trnT-S and trnT-Y) isolated from 90 populations. 19 haplotypes were identified. One of them was shared many of the species that covered the perichaco arc. The other haplotypes were share by different group of species and some of them were privative of species or populations. The network analysis of haplotypes revealed different linages of haplotypes. In the southest the linages were associated with the main river channels of the alluvial megafan generated by the Paraná River during the Upper Quaternary. However, in the Southwest the linages were not associated to river channels, but they suggest dispersion pathways associated to the expansion of the seasonally dry forest.