Systematics Section / ASPT
Feist, Mary Ann , Downie, Stephen R. .
A phylogenetic examination of Oxypolis and Ptilimnium (Apiaceae) using nuclear ribosomal DNA ITS sequences.
The Apiaceae are a large economically important family comprised of approximately 455 genera and 3700 species. Relationships within this large family, especially below the level of tribe, have been poorly understood. Oxypolis and Ptilimnium are two closely related genera within tribe Oenantheae that are endemic to North America. Both are relatively small genera, each with seven or eight species, several infraspecific taxa, and a putative hybrid. Among these taxa are two federally endangered species (Ptilimnium nodosum and Oxypolis canbyi). As is the case with many genera in the Apiaceae, relationships within and between Oxypolis and Ptilimnium are unclear. For example, Ptilimnium nodosum and three species of Oxypolis (O. canbyi, O. filiformis, and O. greenmannii) share an unusual leaf morphology. Rather than having the pinnately compound leaves that generally characterize tribe Oenantheae, they have reduced linear, terete, mostly hollow, septate appendages ("rachis-leaves"). Also, Ptilimnium nodosum is presently recognized as one species, but evidence from previous studies has suggested that it may in fact be a complex of three species. In this study we use nuclear ribosomal DNA ITS data to explore relationships within and between these genera and to examine their position within the tribe. ITS data were obtained for all species and infraspecific taxa for these two genera. Data were analyzed using maximum parsimony and maximum likelihood analyses. Neither Oxypolis nor Ptilimnium as presently defined appear to be monophyletic. Instead, the results suggest that the rachis-leaved taxa from both genera form a monophyletic group which is a sister group to the Ptilimnium taxa with pinnately compound leaves. Oxypolis species with pinnately compound leaves form a third, but more distantly related monophyletic group. In addition, several of the infrageneric taxa appear to be improperly delimited.
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1 - University of Illinois Urbana, Department of Plant Biology, 265 Morrill Hall, 505 South Goodwin Avenue, Urbana, Illinois, 61801-3707, USA
2 - University of Illinois Urbana, Department of Plant Biology, 239 Morrill Hall, 505 South Goodwin Avenue, Urbana, Illinois, 61801-3707, USA
Presentation Type: Oral Paper
Date: Wednesday, August 17th, 2005
Time: 8:00 AM