Phylogenetic analysis of chloroplast rps16 intron sequences reveals relationships within the woody southern African Apiaceae subfamily Apioideae

Evolutionary relationships among 48 genera of Apiaceae (Umbelliferae) were inferred using maximum parsimony, maximum-likelihood, and neighbor-joining analyses of chloroplast DNA rps16 intron and adjacent rps16 3′ exon sequences. Emphasis was placed on woody members of Apiaceae subfamily Apioideae endemic to southern Africa, a region hypothesized to be the place of origin of this largely herbaceous subfamily. The resultant phylogenies were highly concordant and indicate that the apioid genera Polemanniopsis and Steganotaenia form a clade sister to Apiaceae subfamily Saniculoideae. The African genera Anginon, Dracosciadium, Glia, Heteromorpha, and Polemannia also comprise a clade and likely represent the most basal elements within Apioideae. Heteromorpha, however, is not monophyletic, with Heteromorpha arborescens (Spreng.) Cham. & Schltdl. var. abyssinica (A. Rich.) H. Wolff and Heteromorpha arborescens (Spreng.) Cham. & Schltdl. var. arborescens arising in separate subclades. Progressing up the trees, Annesorhiza then Bupleurum fall as successive sister taxa to all remaining Apioideae. The major clades recognized within subfamily Apioideae are largely congruent with those inferred using other types of molecular evidence. Sequence divergence is similar to that of other chloroplast introns, including being generally low among congeners and woody taxa. While the rps16 intron has seen very little use in molecular systematic studies to date, this study demonstrates its ability to discern high-level relationships within Apiaceae.