A molecular phylogeny of Apiaceae tribe Caucalideae and related taxa: inferences based on ITS sequence data

Since the tribe Caucalideae was recognized by Bentham and later Boissier for those species of Apiaceae (Umbelliferae) with spines, hooks, tubercles or bristly hairs on the primary and/or secondary ridges of their fruits, there has been considerable disagreement as to its proper circumscription, the relationships among its members, and the delimitation of certain genera. A recent checklist of the group recognized 68 species in 21 genera; a previous molecular systematic study, however, excluded Aphanopleura and Psammogeton from the tribe. Phylogenetic relationships among all but one of the 19 remaining genera (material from the rare, monotypic genus Angoseseli was not available for examination) and representatives from putatively allied tribes Scandiceae, Laserpitieae, Apieae and Smyrnieae were inferred from nucleotide sequence variation in the internal transcribed spacer regions of 18S-26S nuclear ribosomal DNA. In all, 29 genera representing 58 taxa were examined. Phylogenies estimated using maximum parsimony, maximum likelihood, and neighbor-joining methods give trees of essentially similar topology, and reveal three major lineages of equivocal relationship: (1) Agrocharis, Ammodaucus, Artedia, Cuminum, Daucus, Laser, Laserpitium, Orlaya, Polyophium, Pseudorlaya, and Pachyctenium; (2) Astrodaucus, Caucalis, Chaetosciadium, Glochidotheca, Lisaea, Szovitsia, Torilis, Turgenia, and Yabea; and (3) Anthriscus, Kozlovia, Myrrhis, Osmorhiza, and Scandix. These groups are provisionally named the Daucus, Torilis, and Scandix subclades, respectively, of a previously delimited Daucus clade. The first subclade contains representatives of Drude's tribe Laserpitieae, whereas the third subclade coincides with Heywood's tribe Scandiceae. Based on those species included in the study, the genera Daucus, Laserpitium, and Torilis are each not monophyletic.