An analysis was made of the evolutionary relationships of the "Delostylis Group" of Trillium. Although this Rafinesquian genus was never accepted, the name can be used to define a group consisting of Trillium catesbaei, T. nivale, T. persistens, and T. pusillum; the defining feature of this group is the style which is basally fused. Recent phylogenetic analyses of Trilliaceae have suggested that, based on morphology, it may represent a distinct group, either within Trillium or as a sister group to it. A comprehensive analysis of the "Delostylis Group" as part of phylogenetic studies of Trilliaceae has not been possible previously because molecular data were available for only one of its species, T. pusillum. The status and relationships of the "Delostylis Group" of Trillium were evaluated based on comparisons of morphological and molecular phylogenetic data (ITS and matK) for several varieties of T. pusillum as well as for the other species in this group.

Key words: Delostylis, DNA sequence data, morphological data, phylogenetic analysis, Trilliaceae, Trillium