Chromosome numbers of some North American species of <i>Artemisia</i> (Asteraceae)

Abstract

Chromosome number determinations are reported for 58 accessions, comprising 13 native and introduced taxa of Artemisia found in Canada and the United States. Chromosome numbers observed were n = 8, 9, 18, and 27. A chromosome number of 2n = 18 is the first report for A. pacifica Nutt. A new tetraploid cytotype (2n = 36) was found in A. frigida Willd. Supernumerary chromosomes (n = 9 + 3) and mixoploidy (n = 18, 36) were also observed in this taxon for the first time. Heteroploidy was present in several species. In some taxa, morphological or ecological differences between the chromosomal races were detected; in other cases no differences were noted. Karylogical and phylogenetic evidence is presented for the original chromosome number in Artemisia having been x = 9.