Chromosome numbers within the Achillea millefolium and the A-distans groups in the Czech Republic and Slovakia

The Achillea millefolium group is represented in the Czech Republic and Slovakia by six species. Achillea setacea and A. asplenifolia are diploid: A. collina and A. pratensis are tetraploid; A. millefolium is hexaploid; and A. pannonica is octoploid. The populations from Slovakia of the A. distans group, distributed mainly in Central and south-eastern Europe, were all hexaploid. The presence of these taxa in the area studied was documented by means of chromosome counts in 285 plants originating from 110 mainly natural populations. Results of the chromosome counts are discussed against a background of literature data from Europe. For the species studied, brief descriptions as well as comments on their distribution and ecology are provided.