Molecular phylogeny and evolution of floral characters of Artemisia and allies (Anthemideae, Asteraceae): evidence from nrDNA ETS and ITS sequences

Abstract

To better understand the evolutionary history of the genus Artemisia (Anthemideae, Asteraceae) and its relationships to other genera of the subtribes Artemisiinae, Leucantheminae and Tanacetinae, 63 sequences of the external and 10 of the internal transcribed spacer of nuclear ribosomal DNA (ETS and ITS) were newly generated. Analyses were performed on the combined dataset using maximum parsimony, maximum likelihood and Bayesian inference. The combined analysis supports that all Artemisiinae genera included plus Hippolytia (subtribe Tanacetinae) and Nipponanthemum (subtribe Leucantheminae) constitute a monophyletic group. Within this group, a successive branching shows three monophyletic groups: (I) Nipponanthemuml Hippolytia/Brachanthemum; (2) the Dendranthema group; and (3) the Artemisia/Kaschgaria group. Within the latter, a new sister-group relationship is found between the monophyletic genus Kaschgaria and the Artemisia group, which comprises two main evolutionary lineages: (i) the Dracunculus clade including various Artemisia species and four Asian genera: Filifolium, Mausolea, Neopallasia and Turaniphytum; and (ii) the remaining subgenera of Artemisia plus the two North American genera: Picrothamnus and Sphaeromeria. Within this phylogenetic framework the evolution of two important characters (capitula and pollen type) in the group was inferred. Character reconstruction reveals that discoid capitula and Anthemis pollen type are the ancestral condition in the subtribe. The Artemisia/Kaschgaria lineage probably originated from an ancestor with disciform capitula, central hermaphrodite florets and Artemisia pollen type. Molecular evidence of several biogeographical migration routes of the genus Artemisia is presented.