Hong, Seong Eun , Yoo, Mi-jeong , Kim, Kyeonghee , Park, Chong-wook .
Molecular divergence of disjunct populations of Polygonum sagittatum L. (Polygonaceae) in eastern Asia and eastern North America
Polygonum sagittatum belongs to sect. Echinocaulon Meisn. which includes 21 species and is distinguished from the other species in the section in having broadly lanceolate to oblong leaves with sagittate bases, oblique scarious ocreae, and inflorescences composed of dense headlike clusters of flower fascicles. Polygonum sagittatum shows an interesting disjunct distribution pattern, as the present distribution is confined to eastern Asia and eastern North America. These disjunct populations show slight morphological differentiations in leaf margins and achene surfaces, and their taxonomic status has long been in dispute. In the present study, we examined nrDNA ITS and cpDNA trnL-trnF sequences of 42 accessions representing 38 populations of P. sagittatum in eastern Asia and eastern North America and 16 additional species of sect. Echinocaulon to elucidate the origin and relationships of the two disjunct populations of P. sagittatum. In MP phylogenies inferred from ITS and trnL-trnF sequence datasets, accessions of P. sagittatum formed a strongly supported monophyletic clade, suggesting a common origin of the two geographically separated populations. The P. sagittatum clade further resolved into two sub-clades; the "Eastern Asian sub-clade" and the "Eastern North American sub-clade". The p-distance values between the disjunct populations ranged from 0.02393 to 0.02737 in the ITS region and from 0.00331 to 0.00441 in the trnL-trnF region, indicating that they are genetically diverged. In addition, genetic variation was observed within eastern Asian and eastern North American accessions: Seven ITS and four trnL-trnF haplotypes were detected in eastern Asian accessions, and six ITS and one trnL-trnF haplotypes in the eastern North American ones. However, there were no common haplotypes between the populations of eastern Asia and eastern North America. These results strongly suggest that the populations of P. sagittatum in eastern Asia and eastern North America were separated in the distant past, presumably during the Pleistocene glaciation, and have evolved independently since.
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1 - Seoul National University, School of Biological Sciences, College of Natural Sciences, Seoul, 151-747, Korea
eastern Asian-eastern North American disjuncts
Presentation Type: Poster:Posters for Sections
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM