TAXONOMIC REVIEW OF SYMPHYOTRICHUM PATENS (ASTERACEAE: ASTEREAE)

The eastern North American Symphyotrichum patens has been treated by Jones (1983, 1992) and other botanists to include var. patens, var. patentissimum, and var .gracile. These taxa have been distinguished primarily by habit, involucral size and vestiture, and phyllary orientation. Morphological distinctions between var. patens and var. gracile have been viewed as overlapping and the two taxa have been interpreted as sympatric over a wide region; the present study concludes that it is not possible to distinguish them in an unarbitrary or evolutionarily meaningful way, and var. gracile is not recognized. Variety patens sensu lato apparently comprises two diploid and three or four tetraploid population systems. Variety patentissimum is morphologically distinct and consistently tetraploid, and it intergrades with tetraploid var. patens where their ranges are contiguous or overlapping. A county-level map shows the distribution of the two infraspecific taxa of S. patens, as interpreted in the present study. A similar map shows ploidal distribution within the species, based on data available from previous studies.