Systematics Section / ASPT
Kim, Sang-Tae , Donoghue, Michael J. .
Allopolyploid speciation in Persicaria (Polygonaceae).
Persicaria (L.) Mill. consists of ca. 100 species of weedy herbs found in moist or disturbed areas. Phylogenetic analyses were conducted using nuclear ITS and chloroplast DNA (partial matK, psbA-trnH IGS and trnL-F) sequences from 60 accessions representing 45 species, with an emphasis on section Persicaria. Our results revealed a number of conflicts in tree topology between nrITS and cpDNA phylogeny, suggesting possible instances of hybrid speciation. However, we might be underestimating hybridization events due to the concerted evolution in nrITS, or overestimating due to the cytoplasmic introgression or lineage sorting. To address these possibilities we used the second intron of the nuclear single copy gene, LEAFY (PL2INT), and our sequence analyses provided more direct evidence of hybrid speciation involving allopolyploidy. We found distinct copies of PL2INT sequences in polyploid species, generally consistent in number with ploidy level. The different copies of PL2INT from polyploid species clustered with sequences from the two different diploid species that were hypothesized as parental lineages. Furthermore, our PL2INT sequence analyses revealed more hybrid speciation events than hypothesized based on incongruence between nrITS and chloroplast gene trees, and clarified the direction of concerted evolution in nrITS. The combination of DNA sequence analyses with distribution patterns and chromosome counts points to the importance of hybridization and allopolyploid speciation in the diversification of Persicaria.
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1 - Yale University, Department Ecology & Evolutionary Biology, Po Box 208105, New Haven, Connecticut, 06520-8105, USA
LEAFY second intron
Presentation Type: Oral Paper:Papers for Sections
Location: International Ballroom South/Hilton
Date: Wednesday, July 11th, 2007
Time: 4:05 PM