The cytogeography of Asterpilosus (Compositae): Ontario and the adjacent United States

The chromosome numbers of individuals from 48 sites in southern Ontario and 12 sites in the eastern U.S.A. were determined. Twenty-one populations in Ontario of Aster pilosus var. pringlei were found to be hexaploid with 2n = 48 (first report for taxon). Sixteen populations of Aster pilosus var. pilosus were tetraploid 2n = 32 (first report for this ploidy level) and 11 populations were hexaploid 2n = 48. In southwestern Ontario, hexaploids of var. pilosus were found concentrated in one region on glacial sand, till soils, and coarse gravel fill, while tetraploids were only found on finer textured silt plains and limestone outcropping. In Ontario, the two varieties are nearly allopatric, only growing in close proximity on Presqu'ile Point on Lake Ontario. Both tetraploid and hexaploid plants of var. pilosus were found in the United States. The hexaploids were common near the Great Lakes but rare further south. Aster pilosus var. demotus was treated as a synonym of var. pilosus, since nearly glabrous plants...