Liatris is a genus occurring in North American grasslands that includes several widespread, variable species as well as numerous localized endemics, some of conservation concern. It is known for its difficult taxonomy and putative hybridization and introgression. In her comprehensive treatment of the genus, Gaiser (1946) recognized 32 species in two sections and 10 series. Since that time, several new species have been described, and some species recognized by Gaiser have been lumped with other taxa or recognized at different levels. Taxonomic and evolutionary studies of particular Liatris taxa and species groups are intriguing and highlight the potential value of a modern phylogenetic framework for the entire genus. Preliminary phylogenetic data based on sequences from the nuclear (the ITS region of nrDNA) and chloroplast (the trnL-F spacer region) genomes are presented, and discussed in light of the current taxonomy. Morphological characters that have been emphasized historically in the group (e.g., nature of the phyllaries, shape of involucre, pappus morphology, pubescence in the corollas) are considered, with particular attention to the species with a plumose pappus. The challenge of detecting adequate levels of sequence variation is addressed, with discussion of additional molecular markers that will be investigated.

Key words: Eupatorieae, ITS, Liatrinae, Liatris, phylogeny, trnL-F