, Volume 27, Issue 2, pp 187–196

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

  • Ronald J. Tyrl


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.


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Copyright information

© The New York Botanical Garden 1975

Authors and Affiliations

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

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