XVI International Botanical Congess

N-European lymegrass (Leymus arenarius, Poaceae) and its two morphologically similar species, namely N-American/N-Pacific L. mollis and central Eurasian L. racemosus, were examined using amplified fragment length polymorphism (AFLP) of the whole genome, restriction fragment length polymorphism (RFLP) and fluorescence in situ hybridization of the 18S-26S ribosomal genes. These approaches have clearly differentiated the octoploid L. arenarius (2n = 56, Icelandic) and the tetraploid L. mollis (2n = 28, Alaskan). The Icelandic lymegrass is more homogeneous than the Alaskan material, and the molecular profiles indicate that the former is probably of recent (post-glacial) origin, whereas the latter is much older and has diverged into sub-species. The N-European L. arenarius, on the other hand, is more closely related to the tetraploid Eurasian L. racemosus, such that the former must have originated from the latter, either by auto- or allopolyploidy.