Phylogenetic analyses of DNA sequence data were undertaken to address systematic questions involving subtribe Liatrinae. Molecular phylogenetic results placed Liatrinae among the relatively derived x = 10 lineage of Eupatorieae as sister to the Eupatorium + Eupatoriadelphus clade. This result is in agreement with biogeographic distributions (the two clades are unique in Eupatorieae for their distributions centered in eastern North America), although not with traditional taxonomic treatment. Molecular results supported separation of Trilisa and Litrisa as distinct from Carphephorus, and also provided confirming evidence for placement of the anomalous Garberia and Hartwrightia within Liatrinae. The shrubby Garberia is placed basally as the sister group to the remainder of the otherwise herbaceous subtribe. There is, however, incongruence in the placement of Hartwrightia. Results based on the chloroplast encoded matK placed it as sister to Carphephorus, whereas those based on the nuclear ITS placed it with Trilisa. Combined matK + ITS results for the entire subtribe gave little resolution, but with Hartwrightia (and Litrisa, another anomalous genus) removed, there was strong support for a sister group relationship between Liatris and Carphephorus, with Trilisa sister to that clade. Hartwrightia may thus be an example of a morphologically distinct genus that has arisen through phylogenetic reticulation.

Key words: Asteraceae, Eupatorieae, ITS, molecular phylogenetics, phylogenetic reticulation