Phylogeography of Eriotheca species complex: insights into the origin and range expansion of apomictic and polyploid trees in Neotropical Savannas.

Polyploidy and whole genome duplication are major evolutionary drivers in plants. Climate variations during the Pleistocene have influenced distribution and range expansion worldwide. Similar trends have been reported for Cerrado plants, but no attempt has been made to link phylogeography with ploidy and breeding changes. Thus, we aimed here (1) to assess ploidy and genome size of Eriotheca estevesiae Carv.-Sobr., and compare it with E. pubescens (Mart.) Schott & Endl. (Both included into the Eriotheca Stellate Trichome Species Complex - ESTSC). (2) Subsequently, we investigated their phylogeography to see whether genetic structure and range expansion trends were similar to those previously described for the Cerrado biome. Finally (3), we discussed whether ESTSC phylogeographical patterns could be associated to geographical parthenogenesis processes. Common cytogenetic techniques and flow cytometry were used to confirm chromosome number and genome size of E. estevesiae. We used three cpDNA regions to analyse 14 ESTSC Cerrado populations, for which we obtained also ploidy level and breeding information. We investigated haplotype diversity, population structure and tested neutrality, aiming at reconstructing phylogeographic scenarios. We found three ploidy levels and eight cpDNA haplotypes in ESTSC, one of them shared by most populations. Haplotype and ploidy distribution corroborated the idea that E. pubescens, the widely distributed polyploid and apomictic species, may have originated from northern diploid and probably sexual E. estevesiae. Matrilinear cpDNA links support the idea that apomixis and polyploidy in ESTSC may have allowed range expansion during the Pleistocene, in a process analogous to the geographic parthenogenesis described elsewhere.