Origin and distribution of polyploid Achillea (Compositae) in western North America
- Cite this article as:
- Tyrl, R.J. Brittonia (1975) 27: 187. doi:10.2307/2805480
The tetraploid and hexaploid cytotypes ofAchillea millefolium in western North America exhibit a complex distributional pattern involving overlapping ranges, mixed populations, and occasional pentaploid, septaploid, and octoploid plants. Cytogenetic and distributional evidence support the hypothesis that there has been a repeated autoploid origin of hexaploids from tetraploid progenitors. It is suggested that chromosome number differences should not be relied on as markers for infraspecific taxa in this complex.