A phylogenetic approach is being used to investigate the evolution and biogeographical history of the polyploid Andean genus Tarasa (Malvaceae). Members of the genus are characterized by their blue or purple flowers (sometimes white) displayed in axillary scorpioid cymes, with apically aristate, completely dehiscent mericarps, and a base chromosome number of x=5. The 30 species exhibit a complex biogeographical pattern involving elevational separation of ploidy levels in the Andes, endemism, and long distance disjunctions. The polyploid species of the genus are particularly unusual in that all are annuals and have reduced floral morphologies as compared to the diploid species. A preliminary phylogeny was reconstructed using ITS sequence data from species of Tarasa and other Andean and lowland South American genera also traditionally placed in the Sphaeralcea alliance. Our preliminary results indicate that the tetraploid species of Tarasa form a monophyletic group but that the genus may not be monophyletic. The placement of the closely allied genera Sphaeralcea and Nototriche within the Tarasa clade was particularly surprising. The relationship among these three genera will be discussed with regard to morphology and geographic distribution. The findings from the nuclear-based phylogeny will be compared with a phylogeny inferred from a non-coding chloroplast region.

Key words: Andes, biogeography, Malvaceae, phylogeny, polyploidy, Tarasa