Molecular phylogeny of Chrysanthemum, Ajania and its allies (Anthemideae, Asteraceae) as inferred from nuclear ribosomal ITS and chloroplast trnL-F IGS sequences

To better understand the evolutionary history, intergeneric relationships and circumscription of Chrysanthemum and Ajania and the taxonomic position of some small Asian genera (Anthemideae, Asteraceae), the sequences of the nuclear ribosomal internal transcribed spacer (nrDNA ITS) and the chloroplast trnL-F intergenic spacer (cpDNA IGS) were newly obtained for 48 taxa and combined with those already deposited in GenBank. Phylogenies with an emphasis on Chrysanthemum, Ajania and its allies, by both maximum parsimony and Bayesian analysis, were constructed using either the ITS sequence alone, the IGS sequence alone or combined sequences. The IGS sequence was low phylogenetically informative, but some deletions and insertions were informative for interspecific and intergeneric delimitations. The ITS and the ITS/IGS phylogenies both suggested the presence of two major clades. The monophyly of subtribe Artemisiinae (clade A) could be retrieved when the phylogenetic positions of some ambiguous taxa were renewedly considered. Subtribe Artemisiinae was chiefly divided into two groups, (1) one corresponding to Chrysanthemum, Arctanthemum, Ajania, Opisthopappus and Elachanthemum (the Chrysanthemum group), (2) another to Artemisia, Crossostephium, Neopallasia and Sphaeromeria (the Artemisia group). Within the Chrysanthemum group, Chrysanthemum Arctanthemum and Ajania were closely related to each other, and the generic circumscription was ambiguous; Phaeostigma was excluded from this group that was also confirmed by the 6-bp insertion in the IGS sequence; radiate or rare discoid Brachanthemum was excluded, and discoid Elachanthemum without ray florets was added to this group; at the same time, Opisthopappus in subtribe Tanacetinae should be transferred to subtribe Artemisiinae and became one of the components of the Chrysanthemum group. Based on the molecular phylogenetic framework, the evolution of pollen and capitulum characters was inferred.