The cytogeography of Aster lanceolatus. II. A preliminary survey of the range including A. hesperius

Abstract

Aster lanceolatus has been reported to occur at five ploidy levels in at least some parts of its range: 2n = 32, 40, 48, 56, and 64. Chromosome number determinations from 127 populations from throughout the range are reported here. Octoploid plants were frequent from Nova Scotia to Virginia and across to the Great Plains. Hexaploids were predominant in some northern parts of the range, but very rare or absent in the southern portions. Tetraploids occurred sporadically in the northeast, were common in parts of southern Ontario and Michigan, and were not found in the southern parts of the range. Odd-level polyploids occurred rarely in areas where two even ploidy levels were sympatric. On the Great Plains A. lanceolatus intergraded with A. hesperius with which it is perhaps conspecific. Thirty-four hexaploid and octoploid populations of this western "species" were found in two transects across the northern portion of the prairies and from scattered montane and southern locations. Octoploids were frequent in the western areas while hexaploids were frequent in the northeastern area. Some aneuploidy was found in the montane populations of octoploids. One decaploid 2n = 80 population was found in Wisconsin that is best labelled as A. coerulescens DC. sensu Rosendahl and Cronquist.