A biosystematic study of the Solidago canadensis (Compositae) complex. I. The Ontario populations

Abstract

Populations from 138 locations in Ontario were sampled and found to contain three levels of polyploidy: diploid, tetraploid, andhexaploid. Five taxa are recognized: Solidago canadensis Linn. var. canadensis (2n = 18) and var. hargeri Fem. (2n = 18), S. gigantea Ait. (2n = 18 and 36), S. altissima Linn. (2n = 54), and S. lepida DC. (2n = 54). All are obligate outbreeders and are pollinated by a wide range of insects. The four species are separated by major genetic barriers and attempts to cross them have not been successful except in the case of S. altissima and S. lepida where a single hybrid plant has been raised. The two varieties of S. canadensis are interfertile and intergrade in nature. The two cytotypes of S. gigantea appear to be morphologically inseparable but are genetically isolated. Solidago canadensis var. canadensis and S. altissima are abundant, widespread, and aggressive weeds. Solidago canadensis var. hargeri grows in deciduous woodland in the south of the province. Solidago gigantea grows in wet situations, the tetraploid being of widespread occurrence and the diploid confined to the southeast of the province. Solidago lepida only occurs in northern Ontario.