Artemisia ludoviciana and its allies comprise a complex of 10 species including 7 subspecies. These are endemic to western North America west of the Mississippi River from the Aleutian Islands to Oaxaca Mexico, with greatest diversity in the Pacific Northwest. The complex is highly diverse morphologically and the various forms intergrade perhaps as a result of polyploidy, hybridization and/or recent divergence. Overlap of species boundaries has led to troubled taxonomy and made the production of keys with species decisive couplets nearly impossible. We constructed phylogenies using internal transcribed spacers 1 and 2 (ITS) and 3' end external transcribed spacer (ETS) regions of nuclear ribosomal DNA (rDNA) to 1) determine the phylogenetic placement of the complex within the genus Artemisia, 2) determine the relationship of the native North American taxa and their putative Eurasian relatives, and 3) examine relationships amongst the nominal forms. Our analysis resulted in the North American taxa forming a highly supported clade within series Artemisia (sensu lato) and show a sister relationship to the Eurasian taxa sampled including the North American species Artemisia palmeri. We found a low amount of phylogenetically informative sites amongst the ITS sequences of the complex and attribute this to a recent origin of the group.

Key words: Artemisia ludoviciana, Asteraceae, ETS, ITS, phylogeny