Diversification of the North American Doellingeria-Eucephalus Clade (Astereae: Asteraceae) Inferred from Molecular and Morphological Evidence

Abstract— Doellingeria and Eucephalus form the earliest-diverging clade of the North American Astereae lineage. Phylogenetic analyses of both nuclear and plastid sequence data show that the Doellingeria-Eucephalus clade consists of two main subclades that differ from current circumscriptions of the two genera. Doellingeria is the sister group to E. elegans , and the Doellingeria + E. elegans subclade in turn is sister to the subclade containing all remaining species of Eucephalus . In the plastid phylogeny, the two subclades are deeply divergent, a pattern that is consistent with an ancient hybridization event involving ancestral species of the Doellingeria-Eucephalus clade and an ancestral taxon of a related North American or South American group. Divergence of the two Doellingeria-Eucephalus subclades may have occurred in association with northward migration from South American ancestors. We combine these two genera under the older of the two names, Doellingeria , and propose 12 new combinations (10 species and two varieties) for all species of Eucephalus .