Systematics/Phytogeography / Taxonomie/ Section
Feist, Mary Ann , Downie, Stephen R. .
Changes to the generic delimitation of Oxypolis and Ptilimnium (Apiaceae) based on nrDNA ITS and cpDNA sequence data.
Oxypolis and Ptilimnium are two genera within Apiaceae tribe Oenantheae endemic to North America. Both genera are relatively small, each with seven or eight species and several infraspecific taxa. Relationships within and between Oxypolis and Ptilimnium are unclear because of the simplified vegetative morphologies of some species. For example, Ptilimnium nodosum and three species of Oxypolis (O. canbyi, O. filiformis, and O. greenmanii) share an unusual leaf morphology. Rather than having the pinnately compound leaves that generally characterize most members of tribe Oenantheae, they have reduced linear, terete, mostly hollow, septate appendages called rachis-leaves. In a previous study, nrDNA ITS data were used to explore relationships within and between these genera and to examine their position within the tribe. A phylogeny based on these data showed that neither Oxypolis nor Ptilimnium as presently defined is monophyletic. The rachis-leaved Oxypolis species were determined to be more closely related to both the rachis-leaved and compound-leaved Ptilimnium species then they were to their compound-leaved congeners. Also, the North American endemic species Cynosciadium digitatum, Daucosma laciniata, and Limnosciadium pinnatum formed a strongly supported clade with the rachis-leaved Oxypolis and all Ptilimnium species. In the current study, we report results for the group using DNA sequences from two loci of the chloroplast genome (psbI-trnK and petA-psbJ). The results of preliminary phylogenetic analyses of these data are congruent with those obtained from the ITS region. While our study is still in progress, it is clear that changes to the generic delimitations of Oxypolis and Ptilimnium will be inevitable. These changes will be discussed in light of the results of our ongoing studies obtained from phylogenetic analyses of these ITS and cpDNA sequence data.
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1 - University of Illinois at Urbana-Champaign, Department of Plant Biology, 265 Morrill Hall, 505 South Goodwin Avenue, Urbana, Illinois, 61801-3707, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, July 30th, 2008
Time: 2:45 PM