title: Evolutionary and Taxonomic Implications of Variation in Nuclear Genome Size: Lesson from the Grass Genus Anthoxanthum (Poaceae).
abstract: The genus Anthoxanthum (sweet vernal grass, Poaceae) represents a taxonomically intricate polyploid complex with large phenotypic variation and its evolutionary relationships still poorly resolved. In order to get insight into the geographic distribution of ploidy levels and assess the taxonomic value of genome size data, we determined C- and Cx-values in 628 plants representing all currently recognized European species collected from 197 populations in 29 European countries. The flow cytometric estimates were supplemented by conventional chromosome counts. In addition to diploids, we found two low (rare 3x and common 4x) and one high (~16x-18x) polyploid levels. Mean holoploid genome sizes ranged from 5.52 pg in diploid A. alpinum to 44.75 pg in highly polyploid A. amarum, while the size of monoploid genomes ranged from 2.75 pg in tetraploid A. alpinum to 9.19 pg in diploid A. gracile. In contrast to Central and Northern Europe, which harboured only limited cytological variation, a much more complex pattern of genome sizes was revealed in the Mediterranean, particularly in Corsica. Eight taxonomic groups that partly corresponded to traditionally recognized species were delimited based on genome size values and phenotypic variation. Whereas our data supported the merger of A. aristatum and A. ovatum, eastern Mediterranean populations traditionally referred to as diploid A. odoratum were shown to be cytologically distinct, and may represent a new taxon. Autopolyploid origin was suggested for 4x A. alpinum. In contrast, 4x A. odoratum seems to be an allopolyploid, based on the amounts of nuclear DNA. Intraspecific variation in genome size was observed in all recognized species, the most striking example being the A. aristatum/ovatum complex. Altogether, our study showed that genome size can be a useful taxonomic marker in Anthoxathum to not only guide taxonomic decisions but also help resolve evolutionary relationships in this challenging grass genus.
authors.affiliation: Department of Botany, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Chumová
authors.affiliation: Department of Botany, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
authors.forename: Jana
authors.initials: J
authors.lastname: Krejčíková
authors.affiliation: Central-European Institute of Technology, Masaryk University, Brno, Czech Republic.
authors.forename: Terezie
authors.initials: T
authors.lastname: Mandáková
authors.affiliation: Department of Botany, Faculty of Science, Charles University in Prague, Prague, Czech Republic; Institute of Botany, The Czech Academy of Sciences, Průhonice, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Suda
authors.affiliation: Department of Botany, Faculty of Science, Charles University in Prague, Prague, Czech Republic; Institute of Botany, The Czech Academy of Sciences, Průhonice, Czech Republic; Biotechnological Centre, Faculty of Agriculture, University of South Bohemia, České Budějovice, Czech Republic.
authors.forename: Pavel
authors.initials: P
authors.lastname: Trávníček
mesh_terms: D005075:Biological Evolution; D002467:Cell Nucleus / Q000737:chemistry; D032461:Chromosomes, Plant / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D004171:Diploidy; D005060:Europe; D005434:Flow Cytometry; D049810:Genetic Speciation; D018745:Genome, Plant; D006824:Hybridization, Genetic; D063148:Plant Dispersal; D018517:Plant Roots; D006109:Poaceae / Q000145:classification / Q000235:genetics*; D011123:Polyploidy; D013045:Species Specificity
chemical_list: D018744:DNA, Plant