Family Tree of Helenieae (Asteraceae)

Science Center A154

The tribe Helenieae, part of the sunflower family, evolved in southwestern North America and is comprised of 13 genera and 115 species. The taxonomy and generic-level phylogeny of these groups is well-understood thanks to extensive work by Bierner, Baldwin, Wessa, and colleagues. Although the diversity of Helenieae is highest in arid and semiarid ecosystems of western North America, notable exceptions exist: Balduina is endemic to the southeastern United States, most species of Heleneium have a strong affinity for wet soils, and Hymenoxys, Helenium, and Gaillardia have colonized South America, likely via long-distance dispersal. Moreover, species of Helenieae are commonly encountered on gypsum soils in southwestern North America, suggesting an ancestral tolerance of the substrate in the tribe. To understand niche evolution and biogeographic history in Helenieae, we are reconstructing the evolutionary history of the tribe by generating DNA sequences of one nuclear gene region and two chloroplast gene regions for all but 5 species, followed by phylogenetic analysis and character state reconstruction.