One or more species in the arctic grass genus Dupontia? - a contribution to the Panarctic Flora project

The grass family (Poaceae) is the largest family of vascular plants in the Arctic. The family includes several species complexes that show high ploidy levels, predominantly reproduce asexually, are poorly morphologically delimited, and have a possible origin within the Arctic area by reticulate evolution. Challenged by work on the Panarctic Flora project and apparent discrepancies in recent taxonomic treatments, we investigated the arctic grass genus Dupontia by molecular and cytogenetic methods. Identical plastid DNA (trnL-F) sequences and very similar AFLP profiles indicated that Dupontia and Arctophila are closely related and that the latter might have been involved in a possible intergeneric hybrid origin of Dupontia. Despite the presence of intra-individual rDNA (ITS) variation in Dupontia indicating an allopolyploid hybrid origin of the genus, it was not possible to predict the second parental species from sequence data or from fluorescent in situ hybridization (FISH) experiments using genomic probes. Due to lack of sequence divergence within Dupontia, AFLP fingerprinting was applied to investigate whether any genetic subdivision exists within the genus. The data sorted Dupontia first of all according to geography and not to ploidy or morphological characters that have previously been used to discriminate between proposed taxa. The results indicate that the recognition of a single polymorphic species is the best solution for the genus Dupontia.