, Volume 27, Issue 2, pp 187–196

Origin and distribution of polyploid Achillea (Compositae) in western North America

  • Ronald J. Tyrl

DOI: 10.2307/2805480

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.

Copyright information

© The New York Botanical Garden 1975

Authors and Affiliations

  • Ronald J. Tyrl
    • 1
  1. 1.School of Biological SciencesOklahoma State UniversityStillwater