Colloquia: Systematic and Evolutionary Perspectives on Apomixis
Sears, Chris , Whitton, Jeannette .
Laying the foundation for understanding evolutionary relationships within the North American Crepis agamic complex (Asteraceae) using flow cytometry and cpDNA sequence data..
The North American Crepis agamic complex consists of closely related diploid species and a morphologically bewildering array of apomictic polyploid derivatives. Diploids are known in seven of the nine taxonomic species. They are sexual out-crossers with mostly narrow, and always allopatric ranges. Because diploid hybrids are not known to occur, evolutionary relationships among diploids can be determined using traditional phylogenetic methods. In contrast, polyploids are often widely distributed and co-occur with other polyploids and with diploids. Furthermore, polyploids within a taxonomic species are known to reproduce via apomixis and have most likely arisen multiple times throughout the landscape. These issues mean that relationships of polyploids cannot be easily understood using many traditional phylogenetic methods. Prior to our work, the locations of diploid populations in the North American Crepis agamic complex had not been investigate since the publication of Stebbins and Babcock’s monograph of the group in 1938. Given the amount of time that has passed the locations of extant diploid populations was uncertain. Without ploidy level information, one can’t possibly begin to understand the evolutionary relationships and taxonomic circumscriptions within an agamic complex, nor fully appreciate the natural history of individuals and populations. Using flow cytometry conducted on field collected, silica dried leaf tissue we were able to determine the DNA-ploidy for 561 individuals from 111 populations in the North American Crepis agamic complex. We identified populations of diploids in each of the seven taxonomic species that are known to contain diploids. With these data in hand we have been able to resolve relationships amongst diploids using DNA sequence data from the plastid regions rpl16, rps16, trnM-trnS and matK. The approaches and techniques used in this research can be applied to any agamic complex and would be of particular utility to those systems where the identity and distribution of extant diploids and polyploids is not known.
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1 - University of British Columbia, Botany Department, 3529-6270 University Boulevard, Vancouver, British Columbia, V6T 1Z4, Canada
Presentation Type: Symposium or Colloquium Presentation
Location: 551A/Convention Center
Date: Wednesday, August 4th, 2010
Time: 4:15 PM