Chromosome numbers and karyotypes within the genus Achillea (Asteraceae: Anthemideae)

We investigated 28 taxa of the genus Achillea from 85 natural populations. The chromosome numbers of 75 populations are presented for the first time, all showing a basic number of 9 chromosomes. The chromosome numbers of A. alexandri-regis and A. lucana have not previously been reported (both diploid with 2n = 2x = 18). New ploidy levels are reported for A. ageratifolia subsp. ageratifolia (tetraploid with 2n = 4x = 36) and for A. stricta (octoploid with 2n = 8x = 72). B-chromosomes were observed in one population each of A. fraasii and A. holosericea. There are confirmed indications in literature for the other chromosome numbers. The karyotype was investigated for 27 taxa from 79 natural populations. Haploid karyotypes in all taxa of Achillea are highly homogeneous with seven metacentric and two submeta- to subtelocentric chromosomes, the latter with satellites. Karyotypes are indicated for the first time for ten taxa, viz. Achillea alexandri-regis, A. atrata, A. erba-rotta, A. grandifolia, A. lucana, A. macrophylla, A. moschata, A. nana, A. pindicola subsp. integrifolia, A. ptarmica and A. tomentosa. A deviating karyotype was found in plants from one single A. holosericea population. The phylogenetic relevance of cytological data for Achillea is discussed.