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Abstract Detail


Systematics Section / ASPT

Allen, Geraldine A. [1], Black, Scott T A [1].

Molecular evidence concerning the origins of the allopolyploid aster Symphyotrichum ascendens.

SYMPHYOTRICHUM (Aster) ascendens is an allopolyploid (n = 13, 26) aster species of western North America, which originated through hybridization between two distinct Symphyotrichum clades with different base chromosome numbers. Its putative parents are the Great Plains species Symphyotrichum falcatum (n = 5, 10, 15) and the western Cordilleran Symphyotrichum spathulatum (n = 8, 16, 24, 32), each representing separate polyploid complexes in the genus. We sequenced a nuclear DNA region (ITS) and three chloroplast DNA regions (trnL intron, trnL-F spacer, and psbA-trnH spacer) in S. ascendens, S. falcatum and S. spathulatum accessions of known chromosome number. The ITS sequences of S. ascendens had much greater similarity to those of S. spathulatum than to those of S. falcatum. The trnL intron and trnL-F spacer regions exhibited little variation, with no fixed differences among the three species. The psbA-trnH spacer was more variable, with 14 informative characters (10 indels and 4 base substitutions). Some psbA-trnH sequences obtained for S. ascendens resembled those of S. falcatum but others resembled those of S. spathulatum,indicating that allotetraploid (n = 13) races ofS. ascendens originated from at least two hybridization events. The psbA-trnH sequences of one of the parent species, S. spathulatum, were also highly variable and suggested that this species could itself have hybrid ancestry.


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1 - University of Victoria, Department of Biology, P.O. Box 3020 STN CSC, Victoria, British Columbia, V8W 3N5, Canada

Keywords:
polyploidy
hybrid speciation
North American asters
ITS
chloroplast DNA.

Presentation Type: Oral Paper:Papers for Sections
Session: 74-11
Location: 120/Ayres
Date: Wednesday, August 2nd, 2006
Time: 4:00 PM
Abstract ID:701


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