Molecular phylogenetic analysis of members of <I>Chrysanthemum</I> and its related genera in the tribe Anthemideae, the Asteraceae in East Asia on the basis of the internal transcribed spacer (ITS) region and the external transcribed spacer (ETS) region of nrDNA

Abstract

The internal transcribed spacer (ITS) and external transcribed spacer (ETS) regions of nuclear ribosomal DNA (nrDNA) in 30 species and four varieties of Chrysanthemum and 54 species and one variety in the closely related genera within the tribe Anthemideae, the family Asteraceae are sequenced and analyzed to clarify and justify their molecular characteristics and close relationships. Chrysanthemum forms a polytomy clade with Ajania. In addition, the substitution rates of the ITS and ETS regions of Chrysanthemum and Ajania are quite low as compared with the closely related genera. Chrysanthemum and Ajania are too close to separate from each other and have been currently, taxonomically treated as Chrysanthemum in combination. The species of Chrysanthemum studies are highly adapted and diversified with low level DNA divergence and thus, they might have reticulation and/or introgression event during evolutional process. According to the intergeneric mean of Chrysanthemum, a part of the radiate genera and species such as Ajania members studied, Elachanthemum intricatum and Phaeostigma variifolium are placed in the Chrysanthemum clade. However, C. sinuatum is excluded from this clade. The species of Chrysanthemum studied showed so close, relationships with cryptic differences in ITS and ETS with each other and thus, they could be distinctly separated from the other closely related genera in the tribe Anthemideae.