CONICET | Buscador de Institutos y Recursos Humanos

In the last ten years, botanical collections of Arachis species have been intensified in Bolivia. Several new species have been discovered with some very interesting characters, and the range of geographic distribution was expanded for many of known taxa. In the same period the species of section Arachis were re-arranged in six different genomes and in three karyotypic subgroups. In this study we analyzed the distribution of the Arachis section species and the variability of chloroplast sequences (trnT?S and trnT?Y) in order to understand the dispersal pathways and to shed light on the evolutionary history of the section. The range distribution of the species showed a biogeographic segregation of most of the genome and karyotype groups. Most of them were associated to different biogeographic regions and river basins but the chloroplast haplotypes recovered from the species did not. The major diversity of haplotypes was concentrated in the Chiquitanía region, in the San Ignacio Planalto. Two central haplotypes were recognized, one of them for the A genome species and the other for the B, D, K, F and G genomes. Both central haplotypes were widely distributed, covering most of the species range. The remaining haplotypes (19) were more restricted or specific to particular populations. The patterns of species and haplotype distributions, together with the analyses of main paleochannels in central South America, suggests that hydrochory may have played a key role in long distance dispersal and establishment of founders in allopatry. Genome differentiation may have occurred in different river basins during Pliocene, while speciation within each genome may have occurred also in isolation with incomplete linage sorting for the markers analyzed.