title: Cytotype diversity and genome size variation in Knautia (Caprifoliaceae, Dipsacoideae).
abstract: BACKGROUND
  Polyploidisation is one of the most important mechanisms in the evolution of angiosperms. As in many other genera, formation of polyploids has significantly contributed to diversification and radiation of Knautia (Caprifoliaceae, Dipsacoideae). Comprehensive studies of fine- and broad-scale patterns of ploidy and genome size (GS) variation are, however, still limited to relatively few genera and little is known about the geographic distribution of ploidy levels within these genera. Here, we explore ploidy and GS variation in Knautia based on a near-complete taxonomic and comprehensive geographic sampling.
  
  
  RESULTS
  Genome size is a reliable indicator of ploidy level in Knautia, even if monoploid genome downsizing is observed in the polyploid cytotypes. Twenty-four species studied are diploid, 16 tetraploid and two hexaploid, whereas ten species possess two, and two species possess three ploidy levels. Di- and tetraploids are distributed across most of the distribution area of Knautia, while hexaploids were sampled in the Balkan and Iberian Peninsulas and the Alps.
  
  
  CONCLUSIONS
  We show that the frequency of polyploidisation is unevenly distributed in Knautia both in a geographic and phylogenetic context. Monoploid GS varies considerably among three evolutionary lineages (sections) of Knautia, but also within sections Trichera and Tricheroides, as well as within some of the species. Although the exact causes of this variation remain elusive, we demonstrate that monoploid GS increases significantly towards the limits of the genus' distribution.
authors.affiliation: Institute of Botany, University of Innsbruck, Sternwartestraße 15, A-6020, Innsbruck, Austria.
authors.forename: Božo
authors.initials: B
authors.lastname: Frajman
authors.affiliation: Faculty of Science, University of Zagreb, Marulićev trg 20/II, HR-10000, Zagreb, Croatia.
authors.forename: Ivana
authors.initials: I
authors.lastname: Rešetnik
authors.affiliation: Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030, Vienna, Austria. hanna.schneeweiss@univie.ac.at.
authors.forename: Hanna
authors.initials: H
authors.lastname: Weiss-Schneeweiss
authors.affiliation: Department of Botany and Biodiversity Research, University of Vienna, Rennweg 14, A-1030, Vienna, Austria.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Ehrendorfer
authors.affiliation: Institute of Botany, University of Innsbruck, Sternwartestraße 15, A-6020, Innsbruck, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Schönswetter
mesh_terms: D005075:Biological Evolution; D027922:Caprifoliaceae / Q000145:classification / Q000166:cytology / Q000235:genetics*; D032461:Chromosomes, Plant; D059646:Genome Size; D019684:Magnoliopsida / Q000166:cytology / Q000235:genetics; D010802:Phylogeny; D011123:Polyploidy