Phylogenetic analysis of apiaceae subfamily apioideae using nucleotide sequences from the chloroplast rpoC1 intron

Phylogenetic relationships among 25 members of Apiaceae (Umbelliferae) subfamily Apioideae, representing 7 of the 8 tribes and 8 of the 10 subtribes traditionally recognized in the subfamily, and 5 outgroups from Apiaceae subfamilies Hydrocotyloideae and Saniculoideae and allied families Araliaceae and Pittosporaceae have been inferred from nucleotide sequence variation in the intron of the chloroplast gene RNA polymerase C1 (rpoC1). Sequence divergence values in pairwise comparisons of unambiguous positions among all taxa ranged from 0 to 11.3% of nucleotides and averaged 3.8%. Trees derived from rpoC1 intron sequences estimated using maximum parsimony or maximum likelihood methods are of essentially similar topology, and indicate that (1) subfamily Apioideae, with Heteromorpha as its most basal element, is monophyletic and is a sister-group to Eryngium, the only representative examined of Apiaceae subfamily Saniculoideae, (2) Aralia (Araliaceae) arises from within a paraphyletic Apiaceae subfamily Hydrocotyloideae (represented by Centella and Hydrocotyle) and this clade is a sister-group to Apioideae+Saniculoideae, (3) there is a major phylogenetic division within Apioideae (excluding the basal Heteromorpha), with one clade comprising the genus Smyrnium and those taxa traditionally grouped in tribes Dauceae, Scandiceae, and Laserpitieae, and the other clade comprising all other examined taxa, and (4) relationships within each of these 2 major clades of Apioideae are largely equivocal owing to the low levels of nucleotide sequence divergence observed. Although rpoC1 intron sequences can provide valuable characters for addressing phylogenetic relationships among the outgroups and distantly related members of Apioideae, they have little power for resolving relationships among closely related taxa.