UBC Theses and Dissertations

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UBC Theses and Dissertations

Systematic investigations into the North American Crepis agamic complex Sears, Christopher James


The North American Crepis (Asteraceae) agamic complex was established as an important early plant system for the systematic study of polyploid agamic complexes. Research conducted over 70 years ago determined that this western North American group consists of seven species comprising diploids and polyploids, and two species comprising only polyploids. Geographical parthenogenesis is pronounced with six of the seven diploids having restricted ranges in either central Washington or northern California. Much of the historic range of the diploids, especially that on valley bottoms, has undergone extensive land-use conversion over the past 70 years so the distribution of extant diploid populations was unknown. Identifying ploidy is of paramount importance to understanding evolutionary relationships in an agamic as well as identify, and circumscribing species. Diploids are the foundation of an agamic complex because all polyploids arise from them. A flow cytometric (FCM) method was modified to work with field-collected silica-dried leaf tissue using propidium iodide. Because of problems with cultivating seedling, obtaining ploidy information from living material was not possible in this group. This FCM breakthrough made a detailed systematic study of the group possible. Maternal relationships were determined between diploids, and between diploids and polyploids using plastid DNA (ptDNA) sequence data. Species were identified and circumscribed by synthesizing information from ploidy variation, maternal relationships, morphology, distribution, and ecology. Flow cytometry identified extant diploid populations for all seven known diploids and revealed a previously unrecognized diploid occurring on edaphic soils in northern ii California. Because this diploid is not morphologically or ecologically similar to any known diploid it was described as a new subspecies. The ptDNA sequence data indicated that the North American Crepis agamic complex is monophyletic, and sister to Crepis runcinata. There is no conclusive evidence of plastid capture among diploids. The two species comprising only polyploids have been recircumscribed, and reduce in rank to subspecies. Five of the seven species comprising diploids and polyploids have been recircumscribed by synthesizing new information from ploidy variation, maternal relationships, morphology, distribution, and ecology. A new treatment with original keys, descriptions and distribution maps has been produced to reflect these changes.

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