Shrinking the violets:: Phylogenetic relationships of infrageneric groups in Viola (Violaceae) based on internal transcribed spacer DNA sequences

A phylogenetic study of the genus Viola used internal transcribed spacer (ITS) DNA sequences for 44 taxa representing many infrageneric groups in Viola plus outgroups Hybanthus concolor and Noisettia orchidiflora. Parsimony and maximum likelihood approaches place Latin American sections basal in Viola, supporting an Andean origin for the genus. Groups of sect. Chamaemelanium, mostly stemmed and yellow-flowered with x = 6 chromosomes, intermingle with groups of sect. Nomimium that are stemless and white- or blue-flowered with x = 12 or an aneuploid number. Neither section is monophyletic, and the assemblage forms a weak clade or grade, depending on the analysis. The remaining sect. Nomimium groups with primarily blue flowers and x = 10 and aneuploid or polyploid numbers form a clade including Hawaiian sect. Nosphinium, with pansies of sect. Melanium (typically stemmed with multicolored flowers and x = 5 to 17) at the base. Phylogenetic relationships from ITS data herald the need for drastic remodeling of Viola. Proposed changes include splitting sect. Chamaemelanium and some of sect. Nomimium into several sections, transferring the remainder of Nomimium to the segregate sect. Viola, and merging Hawaiian sect. Nosphinium with the amphi-Beringian V. langsdorffii complex under the Langsdorffianae in sect. Viola.