Systematics Section / ASPT
Allphin, Loreen , Windham, M. D. .
Hybridization among western North American Draba (Brassicaceae): The importance of being earnest (about chromosome numbers).
DRABA, the largest genus in Brassicaceae, includes over 350 recognized species. Despite its diversity, the genus is strongly supported as monophyletic in all recent analyses. As in most members of the tribe Arabideae, Draba has a plesiomorphic chromosome base number of x = 8. The basal most branches of the Draba clade are almost exclusively euploid, consisting of diploids (n = 8) and polyploids derived from them. Nested within this euploid grade, is a New World lineage consisting exclusively of polyploids and aneuploids. Early studies by Rollins, Mulligan, etc., discounted the role of hybridization in the evolution of Draba. However, recent studies (Brochmann et al.; Widmer and Baltisberger) on European taxa have revealed extensive hybridization among species belonging to the euploid grade. Funded by the USDA Forest Service, we are conducting extensive morphological, ecological, chromosomal, and genetic studies of western North American Draba. Our work on members of the polyploid/aneuploid clade reveals levels of hybridization comparable to that observed for euploid Draba. For example, D. brachystylis shares many features, including an identical nrDNA ITS sequence, with D. albertina. Our studies indicate that D. brachystylis (n = 22) arose through hybridization between D. albertina (n=12) and an undescribed aneuploid Draba (D. santaquinensis sp. nov.; n=10). Aneuploid to aneuploid hybridization has also been documented in the D. spectabilis and D. lemmonii complexes. In addition, we have evidence of extensive hybridization between euploid and aneuploid Draba, illustrated by the origins of D. crassifolia, D. paucifructa, and D. serpentina comb. nov. These data suggest that reticulation between major clades, previously thought to be rare in Draba, may have played an important role in the evolution of the genus. Chromosome analyses have been critical in our understanding of Draba and should be an important component of any evolutionary study within the genus.
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1 - Brigham Young University, Department of Integrative Biology, 401 Widtsoe Building, Provo, Utah, 84602, USA
2 - University of Utah, Utah Museum of Natural History, 1390 E. President's Circle, Salt Lake City, Utah, 84112, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 134/Performing Arts Center
Date: Tuesday, August 1st, 2006
Time: 11:15 AM