Revised generic delimitations for Oxypolis and Ptilimnium (Apiaceae) based on leaf morphology, comparative fruit anatomy, and phylogenetic analysis of nuclear rDNA ITS and cpDNA trnQ-trnK intergenic spacer sequence data

A phylogenetic study of Oxypolis and Ptilimnium, two small genera of tribe Oenantheae (Apiaceae: subfamily Apioideae), was carried out. Generic circumscriptions and infrageneric and infraspecific relationships were investigated through parsimony and Bayesian inference analyses of nuclear rDNA ITS and cpDNA trnQ-5′rps16 and 3′rps16-5′trnK intergenic spacer sequences. Fruit anatomical characters were also examined and used in conjunction with leaf morphology to corroborate the results of the phylogenetic analyses. Each genus as currently delimited has both compound-leaved and rachis-leaved species. Results of the phylogenetic analyses show that neither Oxypolis nor Ptilimnium is monophyletic; each genus is split into two strongly supported clades that correspond to differences in leaf morphology within the groups. Fruit anatomical characters support these splits. The fruits of compound-leaved and rachis-leaved Oxypolis species differ in the number of commissural vittae per mericarp, the branching of the vittae, and the lignification of mericarp around the seed. The fruits of compound-leaved and rachis-leaved Ptilimnium species differ in the compression of the mericarps and the development of the marginal ribs. The fruits of rachis-leaved Oxypolis and rachis-leaved Ptilimnium species also differ in the compression of the mericarps and the development of the marginal ribs. Based on analyses of molecular data and corroboration with morphological and fruit anatomical data, new circumscriptions for the genera Oxypolis and Ptilimnium are formalized. Each of the two polyphyletic genera (Oxypolis and Ptilimnium) is split, two genera (Tiedemannia and Harperella) are resurrected, and three new combinations are made.