Translator Disclaimer
1 April 2008 A Phylogenetic Study of Oxypolis and Ptilimnium (Apiaceae) Based on Nuclear rDNA ITS Sequences
Author Affiliations +
Abstract

Oxypolis and Ptilimnium are two endemic genera of North America within tribe Oenantheae (Apiaceae subfamily Apioideae). Both genera are small, with 12 species currently recognized. Some members of each genus share an unusual leaf morphology. Rather than having the pinnately compound leaves that generally characterize apioid umbellifers, they have highly reduced, linear, terete, hollow, septate appendages known as rachis leaves. It has long been questioned whether the species with rachis leaves should be placed in separate genera. In this study, we use data from the internal transcribed spacer region of nuclear ribosomal DNA to explore relationships within and between these genera. A total of 147 internal transcribed spacer sequences were obtained from multiple accessions of all species of Oxypolis and Ptilimnium and for several other genera from tribe Oenantheae. These included Lilaeopsis, which also has rachis leaves, and Cynosciadium and Limnosciadium, which have rachis-like leaves. These sequence data were analyzed using maximum parsimony, maximum likelihood, and Bayesian methods. The results from each of these analyses were congruent and suggest that neither Oxypolis nor Ptilimnium as presently defined is monophyletic. Oxypolis and Ptilimnium are each separated into two dades according to leaf morphology. The rachis-leaved Oxypolis species are provisionally recognized as the genus Tiedemannia and the rachis-leaved Ptilimnium species are provisionally recognized as the genus Harperella, pending further investigation. The relationships among these four clades and the genera Cynosciadium, Daucosma, and Limnosciadium are not clear. Nevertheless, it appears that the rachis-leaf habit has evolved multiple times in the tribe. Geographic structure is apparent in the phylogenetic trees and, pending further study, may suggest new taxa; in addition, the presence of O. occidentalis on the Queen Charlotte Islands, well-separated from other populations of this species, suggests that it may have survived the last glaciation in a refugium in this area.

Mary Ann E. Feist and Stephen R. Downie "A Phylogenetic Study of Oxypolis and Ptilimnium (Apiaceae) Based on Nuclear rDNA ITS Sequences," Systematic Botany 33(2), 447-458, (1 April 2008). https://doi.org/10.1600/036364408784571509
Published: 1 April 2008
JOURNAL ARTICLE
12 PAGES


SHARE
ARTICLE IMPACT
RIGHTS & PERMISSIONS
Get copyright permission
Back to Top