Wild Aster lanceolatus × lateriflorus hybrids in Ontario and comments on the origin of A. ontarionis (Compositae–Astereae)

Abstract

Chromosome numbers of putative wild Aster lanceolatus × lateriflorus hybrids were found to be either 2n = 40 or 2n = 48. A comparison of the morphology and chromosome numbers of the putative hybrids, their likely parental species, and A. ontarionis from Ontario revealed that the hybrids were morphologically and cytologically intermediate between A. lanceolatus and A. lateriflorus. The 2n = 40 hybrids were similar to A. ontarionis (2n = 32) but lacked the characteristic leaf pubescence of that species. At one site on the Bruce Peninsula 14 A. lanceolatus plants (2n = 64), 13 A. lateriflorus plants (2n = 32), and one hybrid (2n = 48) were collected and compared in detail. The hybrid was more like A. lanceolatus than the 2n = 40 hybrids from other sites where the A. lanceolatus parents were 2n = 48. The similarities between the putative hybrids and A. ontarionis suggest that this species arose via a hybridization event between A. lanceolatus and A. lateriflorus. Alternative origins are nonetheless possible and these along with the nomenclature of A. lanceolatus are reviewed.