Systematics Section / ASPT
Lamb-Frye, Ann , Kron, Kathleen A. .
Evolutionary relationships in the Polygonella clade (Polygonaceae) based on DNA sequence data.
Polygonella is a distinctive member of the Polygonaceae that occurs in eastern North America. Within the genus approximately 5-9 species have been recognized, with the last revision by Horton in 1961. In the past, Polygonella also has been split into as many as four genera but relationships within this group have not been investigated in a phylogenetic framework. Most of the recognized species of Polygonella are sampled in this study and data are obtained from both chloroplast (matK) and nuclear (ITS) regions. Based on results from a previous study using rbcL, several other polygonaceous species that were found to be related to Polygonella fimbriata var. robusta were included in the analysis. A total of 20 species of Polygonaceae (including our sampled species of Polygonella) were analyzed using parsimony (characters equally weighted, heuristic search, TBR branch swapping). Statistical support for the relationships was assessed using the bootstrap. Data sets were analyzed separately to determine whether there was any strong conflict in topology between the different molecular regions. As none were found, the data were combined for a total evidence analysis. Results indicate that Polygonella is likely monophyletic and is nested deeply within a clade of Polygonaceae that includes Polygonum aviculare and Polygonum erectum. The morphological feature of branches appearing internodal via the sheathing ocrea is a good synapomorphy for the Polygonella clade. Results of this analysis also indicate a close relationship between Polygonum sachilinense, P. japonicum and Atraphaxis spinosa. Interesting patterns of phylogeography were also found given that Polygonella has such a regional geographic distribution. The phylogenetic relationships within the genus Polygonella provide insight into the evolutionary history of this clade within the Polygonaceae; as well as the evolution of these plants in the eastern North America.
1 - Wake Forest University, Department of Biology, P.O. Box 7325, Winston-Salem, North Carolina, 27109-7325, U.S.A.
Presentation Type: Paper
Location: Cottonwood C (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 3:45 PM