YOO, MI-JEONG* and CHONG-WOOK PARK. School of Biological Sciences, Seoul National University, Seoul 151-742, Korea. - Molecular Phylogeny of Polygonum sect. Echinocaulon (Polygonaceae) based on chloroplast and nuclear DNA sequences.
Polygonum sect. Echinocaulon (Polygonaceae) is a highly
variable and taxonomically difficult taxon consisting of 21 species.
The main objectives of this study were to infer phylogenetic
relationships of the taxa within the section, and to provide a
hypothesis on the origin of disjunct distribution pattern of the taxa
based on molecular data. We have examined the ITS and
trnL-trnF sequences from 18 taxa of sect.
Echinocaulon. In all ITS and trnL-trnF trees, the
taxa previously included in the section failed to form a monophyletic
group: P. bungeanum was placed as sister to sect.
Persicaria, suggesting that P. bungeanum should be
transferred from sect. Echinocaulon to sect. Persicaria.
The consensus tree obtained from the combined molecular data sets
revealed the presence of five major lineages in the section; these
include (1) P. perfoliatum-P. senticosum var. senticosum
clade, (2) P. dissitiflorum clade, (3) P. sagittatum
clade, (4) P. dichotomum-P. muricatum clade (seven taxa), and
(5) P. arifolium-P. biconvexum clade (six taxa). Relationships
of the taxa depicted in the consensus tree are, in general, in
agreement with those previously suggested by the comparative flavonoid
chemistry. In addition, the results strongly suggest that P.
sagittatum may once have had a more continuous range in the
northern Hemisphere and fragmented into two widely separated disjunct
populations of eastern Asia and eastern North America during
Key words: Disjunct distribution pattern, ITS, Molecular phylogeny, Polygonum sect. Echinocaulon, trnL-trnF