Systematics Section / ASPT
Noyes, Richard D. , Allison, James R. .
Sexual Erigeron strigosus (Asteraceae) in the southeastern United States.
Erigeron annuus and E. strigosus, are sister taxa, extremely widespread in North America, and heretofore considered to be uniformly apomictic. The recent description of new varieties of E. strigosus in Alabama and Tennessee on rare glade habitats (E. strigosus var. dolomiticola and E. strigosus var. calcicola) and the discovery of a third yet unnamed taxon that is widespread on the piedmont and coastal plain of Georgia (E. strigosus var. nov.) prompted an investigation of the reproductive mode and evolutionary relationships of these taxa. Here, we report that all three varieties are diploid (2n=18) and sexual with tetrasporic megagametophyte development. Analysis of ITS and ETS sequence data for these three taxa shows that E. strigosus var. calcicola occurs basal to E. strigosus var. dolomiticola and E. strigosus var. nov. This supports the hypothesis that the perennial habit of the glade taxa may be ancestral in the group. Eight of 31 populations examined of E. strigosus var. nov. also include polyploid apomictic plants. These mixed populations may provide opportunities for apomictic and sexual plants to interact ecologically and genetically via hybridization. Results suggest that further investigation may reveal additional sexual taxa with restricted geographic distribution in the southeastern United States.
1 - University of Colorado, Department of Ecology and Evolutionary Biology, UCB 334, Boulder, Colorado, 80309-0334, USA
2 - Georgia Department of Natural Resources, Georgia Natural Heritage Program, 2117 US Hwy. 278, SE, Social Circle, Georgia, 30025, USA
Presentation Type: Paper
Location: Cottonwood B (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 12:00 PM