title: Salixtransect of Europe: variation in ploidy and genome size in willow-associated common nettle,Urtica dioicaL.sens. lat., from Greece to arctic Norway.
abstract: BACKGROUND
  The common stinging nettle,Urtica dioicaL. sensu lato, is an invertebrate "superhost", its clonal patches maintaining large populations of insects and molluscs. It is extremely widespread in Europe and highly variable, and two ploidy levels (diploid and tetraploid) are known. However, geographical patterns in cytotype variation require further study.
  
  
  CONCLUSIONS
  We assembled a collection of nettles in conjunction with a transect of Europe from the Aegean to Arctic Norway (primarily conducted to examine the diversity ofSalixandSalix-associated insects). Using flow cytometry to measure genome size, our sample of 29 plants reveals 5 diploids and 24 tetraploids. Two diploids were found in SE Europe (Bulgaria and Romania) and three diploids in S. Finland. More detailed cytotype surveys in these regions are suggested. The tetraploid genome size (2C value) varied between accessions from 2.36 to 2.59 pg. The diploids varied from 1.31 to 1.35 pg per 2C nucleus, equivalent to a haploid genome size of c. 650 Mbp. Within the tetraploids, we find that the most northerly samples (from N. Finland and arctic Norway) have a generally higher genome size. This is possibly indicative of a distinct population in this region.
authors.affiliation: University of British Columbia, Vancouver, Canada.
authors.forename: Quentin
authors.initials: Q
authors.lastname: Cronk
authors.affiliation: Royal Botanic Gardens, Kew, United Kingdom.
authors.forename: Oriane
authors.initials: O
authors.lastname: Hidalgo
authors.affiliation: Royal Botanic Gardens, Kew, United Kingdom.
authors.forename: Jaume
authors.initials: J
authors.lastname: Pellicer
authors.affiliation: Natural History Museum, London, United Kingdom.
authors.forename: Diana
authors.initials: D
authors.lastname: Percy
authors.affiliation: Royal Botanic Gardens, Kew, United Kingdom.
authors.forename: Ilia J
authors.initials: IJ
authors.lastname: Leitch
keywords:  Urtica ; cytotype variation; genome size; megatransect