Systematics Section / ASPT
Burke, Jennifer , Bain, John F .
The evolutionary origins of Erigeron trifidus.
Systematic relationships within the genus Erigeron (Asteraceae: Astereae) remain obscure due to complex geographical distribution patterns, polyploidy, hybridization and agamospermy. Erigeron trifidus Hook. is restricted to three disjunct alpine regions of the Alberta Rocky Mountains and is a designated rare plant in the province. Erigeron trifidus was originally treated as a variety of E. compositus until Packer (1981), based on morphological, cytological and habitat differences, proposed that it be treated as a distinct species and that it had arisen via hybridization between E. compositus and E. lanatus. A restriction site analysis of cpDNA from the three species throughout the range of E. trifidus revealed 4 haplotypes. In most cases cpDNA haplotypes in E. trifidus were the same as in E. lanatus, suggesting E. lanatus as the maternal parent in the majority of crosses. An analysis of the nuclear ETS region further supports the hybrid origin hypothesis in that E. trifidus contains only repeat types present in one or the other of the putative parents. In addition, E. trifidus displays a higher percentage of within individual repeat type polymorphism than either putative parent. ETS and morphological data also reveal a north/south geographic pattern that separates E. trifidus into two groups, possibly indicating a separate origin for southern E. trifidus. Finally, both chloroplast and ETS data sets show a homogenous pattern of genetic variation for E. trifidus across the northern region despite spatial variation for these markers in the parental species. This suggests that northern E. trifidus originated through a single hybridization event and that colonization of the various areas within the northern region occurred post origin.
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1 - University of Lethbridge, Biological Sciences, 4401 University Drive, Lethbridge, Alberta, T1K 3M4, Canada
Presentation Type: Oral Paper
Date: Wednesday, August 17th, 2005
Time: 9:00 AM