A molecular phylogeny of Chinese Apiaceae subfamily Apioideae inferred from nuclear ribosomal DNA internal transcribed spacer sequences

The Hengduan Mountains of the Sino-Himalayas are rich in endemic species of Apiaceae subfamily Apioideae. To investigate relationships among these species and to ascertain their higher-level phylogenetic placements within the subfamily, we examined 106 accessions (representing 100 species from 52 genera) including the Chinese endemic genera Changium, Cyclorhiza, Notopterygium, Nothosmyrnium, and Sinolimprichtia. Sixty-three of these accessions were newly sequenced. Phylogenetic trees were inferred using maximum parsimony and Bayesian analyses of nuclear ribosomal DNA internal transcribed spacer (ITS) sequences. The phylogenetic trees were highly consistent and revealed several major clades heretofore unrecognized in the subfamily. Changium and Cyclorhiza fall within the Komarovia clade of previous investigations and Nothosmyrnium allies with tribe Pimpinelleae. Notopterygium and Sinolimprichtia along with many other taxa of Sino-Himalayan distribution comprise a well-supported East Asia clade; Vicatia and Haplosphaera arise within a paraphyletic Notopterygium. Other newly recognized, well-supported major clades include the Chamaesium clade, sister group to all other examined Apioideae except tribe Bupleureae, and the Asian Acronema clade, sister group to tribe Scandiceae. The Chamaesium clade and Bupleureae may represent the earliest diverging lineages of Apioideae in Asia. Sinodielsia allies weakly with Pterocyclus or is a sister group to the clade of tribe Apieae plus Pterocyclus; Sinodielsia is distinct from Meeboldia and Vicatia. Genera whose boundaries are poorly defined and controversial on the basis of morphology (Ligusticum, Peucedanum, Physospermopsis, Pimpinella, Pleurospermum, Sinocarum, Tongoloa, Trachyspermum) are not monophyletic in the ITS-based phylogenies. Further study of these Chinese endemics is necessary to produce a comprehensive, modern classification of Apiaceae subfamily Apioideae.