Hybridization studies in the aster occidentalis (Asteraceae) polyploid complex of western North America

Hybridization experiments were carried out with 12 of the approximately 15 species in the complex. The crosses involved plants at various ploidy levels from diploid (n=8) to duodecaploid (n=48). Viable F₁ progeny were obtained from 26% of the crosses involving diploids, and from 66% of the crosses between polyploids. All but a few of the progeny had a high degree of pollen fertility, and all of those examined had regular pairing of chromosomes at meiosis. Even at the diploid level few reproductive barriers isolate the taxa of this complex, although morphologically distinct entities can be recognized.