Morphologic characters that have been used to segregate these populations into species and/or varieties include: (1) degree and persistence of tomentum; (2) phyllaries with greenish, light brown, or dark brown margins; (3) shapes of capitulescences (rounded or flat-topped); and (4) degrees of leaf dissection and shapes of lobes.
While examining specimens for this treatment, two general trends were noted: (1) Plants growing either at high latitudes or high elevations tend to have darker colored margins on the phyllaries. (2) Plants at high latitudes or elevations or from extreme desert locations tend to be more densely lanate than plants from less extreme habitats. These are only trends; variations in local populations due to local environmental conditions are to be expected.
An eco-morphotype adapted to the Athabasca sand dunes of northern Saskatchewan has been known as A. megacephala or A. millefolium var. megacephala and has been treated as a taxon of special concern in Canada (V. L. Harms 1999).
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