Species, genomes and diversification in Section Arachis

SEIJO GUILLERMO; SEBASTIÁN SAMOLUCK; CHALUP LAURA; GRABIELE MARINA; GERMAN ROBLEDO

Savannah GA USA

Conferencia; Seventh International Conference of the Peanut Research Community; 2014

Species, genomes and diversification in Section Arachis Guillermo Seijo, Sebastián Samoluk, Laura Chalup, Marina Grabiele and Germán Robledo. Botanical Institute of the Northeast (IBONE, UNNE-CONICET), and Exact and Natural Sciences and Agrimensure Faculty, National University of the Northeast (UNNE). Corrientes, Argentina. 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. The range of geographic distribution was also expanded for many of the 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 analysed the distribution of the Arachis section species and the variability of chlroroplast 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 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 for the A genome species and one for the B, D, K, F and G genomes. Both central haplotypes were widespread, distributed from the center of diversification toward marginal areas covering most of the species range. Other haplotypes (19) were more restricted or privative of 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 analysed.