To study the origin and evolution of naturally occurring polyploids, we performed phylogenetic analyses of nuclear ribosomal DNA spacers combined with molecular cytogenetics in 55 accessions of 27 taxa of the oat genus Helictochloa. A complex pattern of reticulate evolution was revealed with many diploid species and extensive polyploidy up to 20x. Altogether 11 groups of internal transcribed spacer (ITS) sequences can be distinguished. Sequences from 1-3 different ITS lineages were detected in polyploids. Cytogenetic data allow reconstruction of 8 basic monoploid chromosome sets. Six of these genomes occur in different combinations in the polyploid species. Two genomes are only found in diploids. Our sequence and karyological data highlight the occurrence of autopolyploidy and allopolyploidy, provide new information about the evolutionary history of taxa, and allow a more accurate systematic treatment of the concerned species. The geographical distribution of the 11 ITS lineages distinguished is highly structured and points to an origin of the genus in western Asia, presumably in grasslands like steppes or mountain steppes and meadows. The evolutionary basal lineages are of Asian, Minor Asian and east Mediterranean distribution and are present also in North America. The western and central parts of the Mediterranean and northern Europe harbor the modern lineages.

Adams KL, Wendel JF: Polyploidy and genome evolution in plants. Curr Opin Plant Biol 8:135-141 (2005).
Ainouche ML, Baumel A, Salmon A: Spartina anglica C.E. Hubbard: a natural model system for analysing early evolutionary changes that affect allopolyploid genomes. Biol J Linn Soc 82:475-484 (2004).
Ainouche ML, Fortune P, Salmon A, Parisod C, Grandbastien MA, et al: Hybridization, polyploidy and invasion: lessons from Spartina (Poaceae). Biol Invasion 11:1159-1173 (2009).
Alvarez I, Wendel JF: Ribosomal ITS sequences and plant phylogenetic inference. Mol Phylogenet Evol 29:417-434 (2003).
Badaeva ED, Shelukhina OY, Diederichsen A, Loskutov IG, Pukhalskiy VA: Comparative cytogenetic analysis of Avena macrostachya and diploid C-genome Avena species. Genome 53:125-137 (2010a).
Badaeva ED, Shelukhina OY, Goryunova SV, Loskutov IG, Pukhalskiy VA: Phylogenetic relationships of tetraploid AB-genome Avena species evaluated by means of cytogenetic (C-banding and FISH) and RAPD analyses. J Bot, Article ID 742307 (2010b).
Baldwin BG, Sanderson MJ, Porter JM, Wojciechowski MF, Campell CS, Donoghue MJ: The ITS region of nuclear ribosomal DNA: a valuable source of evidence on angiosperm phylogeny. Ann Mo Bot Gard 82:247-277 (1995).
Baum BR, Johnson DA, Bailey LG: Defining orthologous groups among multicopy genes prior to inferring phylogeny, with special emphasis on the Triticeae (Poaceae). Hereditas 135:123-138 (2001).
Baum BR, Edwards T, Johnson DA: Codependence of repetitive sequence classes in genomes: phylogenetic analysis of 5S rDNA families in Hordeum (Triticeae: Poaceae). Genome 53:180-202 (2010).
Blattner FR: Phylogenetic analysis of Hordeum (Poaceae) as inferred by nuclear rDNA sequences (ITS). Mol Phylogenet Evol 33:289-299 (2004).
Blattner FR, Weising K, Baenfer G, Maschwitz U, Fiala B: Molecular analysis of phylogenetic relationships among myrmecophytic Macaranga species (Euphorbiaceae). Mol Phylogenet Evol 19:331-344 (2001).
Campbell CS, Wojciechowski MF, Baldwin BG, Alice LA, Donoghue MJ: Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae). Mol Biol Evol 14:81-90 (1997).
Chester M, Leitch AR, Soltis PS, Soltis DE: Review of the application of modern cytogenetic methods (FISH/GISH) to the study of reticulation (polyploidy/hybridisation). Genes 1:166-192 (2010).
Chester M, Gallagher JP, Symonds VV, Cruz da Silva AV, Mavrodiev EV, et al: Extensive chromosomal variation in a recently formed natural allopolyploid species, Tragopogon miscellus (Asteraceae). Proc Natl Acad Sci USA 109:1176-1181 (2012).
Church SA, Taylor DR: Speciation and hybridization among Houstonia (Rubiaceae) species: the influence of polyploidy on reticulate evolution. Am J Bot 92:1372-1380 (2005).
Comai L, Tyagi AP, Winter K, Holmes-Davis R, Reynolds SH, et al: Phenotypic instability and rapid gene silencing in newly formed Arabidopsis allotetraploids. Plant Cell 12:1551-1568 (2000).
Conert HJ: Gustav Hegi, Illustrierte Flora von Mitteleuropa, vol 1, part 3, ed 3 (Parey Buchverlag, Berlin 1997).
Cronn RC, Cedroni M, Haselkorn T, Grover C, Wendel JF: PCR-mediated recombination in amplification products derived from polyploid cotton. Theor Appl Genet 104:482-489 (2002).
D'Hont A, Ison D, Alix K, Roux C, Glaszmann JG: Determination of basic chromosome numbers in the genus Saccharum by physical mapping of ribosomal RNA genes. Genome 41:221-225 (1998).
Doğan M: Helictotrichon Besser ex Schultes & Schultes fil., in Davis PH (ed): Flora of Turkey and the East Aegean Islands, vol 9, pp 308-313 (Edinburgh University Press, Edinburgh 1985).
Doyle JJ, Doyle JL, Brown AHD, Pfeil BE: Confirmation of shared and divergent genomes in the Glycine tabacina polyploid complex (Leguminosae) using histone H3-D sequences. Syst Bot 25:437-448 (2000).
Doyle JJ, Flagel LE, Paterson AH, Rapp RA, Soltis DE, et al: Evolutionary genetics of genome merger and doubling in plants. Annu Rev Genet 42:443-461 (2008).
Elder JF, Turner BJ: Concerted evolution of repetitive DNA sequences in eukaryotes. Q Rev Biol 70:297-320 (1995).
Feldman M, Liu B, Segal G, Abbo S, Levy AA, Vega JM: Rapid elimination of low-copy DNA sequences in polyploid wheat: a possible mechanism for differentiation of homoeologous chromosomes. Genetics 147:1381-1387 (1997).
Felsenstein J: Confidence limits on phylogenies: an approach using the bootstrap. Evolution 39:784-791 (1985).
Fortune PM, Pourtau N, Viron N, Ainouche ML: Molecular phylogeny and reticulate origins of the polyploid Bromus species from section Genea (Poaceae). Am J Bot 95:454-464 (2008).
Gervais C: Contribution à l'étude cytologique et taxonomique des avoines vivaces. Denkschr Schweiz Akad Naturwiss 88:1-166 (1973).
Grebenstein B, Röser M, Sauer W, Hemleben V: Molecular phylogenetic relationships in Aveneae (Poaceae) species and other grasses as inferred from ITS1 and ITS2 rDNA sequences. Plant Syst Evol 213:133-150 (1998).
Greuter W: The relict element of the flora of Crete and its evolutionary significance, in Valentine DH (ed): Taxonomy, Phytogeography and Evolution, pp 161-177 (Academic Press, London 1972).
Guggisberg A, Baroux C, Grossniklaus U, Conti E: Genomic origin and organization of the allopolyploid Primula egaliksensis investigated by in situ hybridization. Ann Bot 101:919-927 (2008).
Gupta PK, Giband M, Altosaar I: Two molecular probes characterizing the A and C genomes in the genus Avena (oats). Genome 35:916-920 (1992).
Harper JA, Thomas ID, Lovatt JA, Thomas HM: Physical mapping of rDNA sites in possible diploid progenitors of polyploid Festuca species. Plant Syst Evol 245:163-168 (2004).
Harpke D, Peterson A: 5.8S motifs for the identification of pseudogenic ITS regions. Botany 86:300-305 (2008).
Hewitt GM: Some genetic consequences of ice ages, and their role in divergence and speciation. Biol J Linn Soc 58:247-276 (1996).
Holub J: Bemerkungen zur Taxonomie der Gattung Helictotrichon Bess., in Němec B, Klášterský I, Deyl M (eds): Philipp Maxmilian Opiz und seine Bedeutung für die Pflanzentaxonomie, pp 101-133 (Tschechoslowakische Akademie der Wissenschaften, Praha 1958).
Holub J: Helictotrichon Besser; Avenochloa (Dumort.) Dumort, in Tutin TG, Heywood VH, Burges NA, Moore DM, Valentine DH, et al (eds): Flora Europaea, vol 5, pp 208-216 (Cambridge University Press, Cambridge 1980).
Kashkush K, Feldman M, Levy AS: Gene loss, silencing and activation in a newly synthesized wheat allotetraploid. Genetics 160:1651-1659 (2002).
Kotseruba V, Gernand D, Meister A, Houben A: Uniparental loss of ribosomal DNA in the allotetraploid grass Zingeria trichopoda (2n = 8). Genome 46:156-163 (2003).
Kotseruba V, Pistrick K, Blattner FR, Kumke K, Weiss O, et al: The evolution of the hexaploid grass Zingeriakochii (Mez) Tzvel. (2n = 12) was accompanied by complex hybridization and uniparental loss of ribosomal DNA. Mol Phylogenet Evol 56:146-155 (2010).
Kovařík A, Pires JC, Leitch AR, Lim KY, Sherwood AM, et al: Rapid concerted evolution of nuclear ribosomal DNA in two Tragopogon allopolyploids of recent and recurrent origin. Genetics 169:931-944 (2005).
Lange D: Helictotrichon agropyroides (Boiss.) Henrard (Poaceae) - an endemic in S and SE Greece. Bot Chronika (Patras) 10:853-859 (1991).
Lange D: Untersuchungen zur Systematik und Taxonomie der Gattung Helictotrichon Besser ex J.A. Schultes & J.H. Schultes (Poaceae) in Südosteuropa und Vorderasien. Bibl Bot 144:1-238 (1995).
Levan A, Fredga K, Sandberg AA: Nomenclature for centromeric position on chromosomes. Hereditas 52:201-220 (1964).
Levy AA, Feldman M: The impact of polyploidy on grass genome evolution. Plant Physiol 130:1587-1593 (2002).
Lim KY, Matyášek R, Kovařík A, Leitch A: Genome evolution in allotetraploid Nicotiana. Biol J Linn Soc 82:599-606 (2004).
Linares C, González J, Ferrer E, Fominaya A: The use of double fluorescence in situ hybridization to physically map the positions of 5S rDNA genes in relation to the chromosomal location of 18S-5.8S-26S rDNA and a C genome-specific DNA sequence in the genus Avena. Genome 39:535-542 (1996).
Linde-Laursen I, Ibsen E, von Bothmer R, Giese H: Physical location of active and inactive rRNA gene loci in Hordeum marinum ssp. gussoneanum (4x) by in situ hybridization. Genome 35:1032-1036 (1992).
Linder CR, Rieseberg LH: Reconstructing patterns of reticulate evolution in plants. Am J Bot 91:1700-1708 (2004).
Ma Y: Flora Intramongolica, vol 7 (Typis Intramongolicae Popularis, Huhhot 1983).
Mooring JS: Barriers to interbreeding in the Eriophyllum lanatum (Asteraceae, Helenieae) species complex. Am J Bot 88:285-312 (2001).
Parisod C, Alix K, Just J, Petit M, Sarilar M, et al: Impact of transposable elements on the organization and function of allopolyploid genomes. New Phytol 186:37-45 (2010).
Peng YY, Baum B, Ren CZ, Jiang QT, Chen GY, et al: The evolution pattern of rDNA ITS in Avena and phylogenetic relationship of the Avena species (Poaceae: Aveneae). Hereditas 147:183-204 (2010).
Petersen G, Seberg O, Yde M, Berthelsen K: Phylogenetic relationships of Triticum and Aegilops and evidence for the origin of the A, B, and D genomes of common wheat (Triticum aestivum). Mol Phylogenet Evol 39:70-82 (2006).
Petersen G, Aagesen L, Seberg O, Larsen IH: When is enough, enough in phylogenetics? A case in point from Hordeum (Poaceae). Cladistics 27:1-19 (2011).
Pikaard CS: Nucleolar dominance: uniparental gene silencing on a multi-megabase scale in genetic hybrids. Plant Mol Biol 43:163-177 (2000).
Pires JC, Hertweck KL: A renaissance of cytogenetics: studies in polyploidy and chromosomal evolution. Ann Mo Bot Gard 95:275-281 (2008).
Popp M, Oxelman B: Inferring the history of the polyploid Silene aegaea (Caryophyllaceae) using plastid and homoeologous nuclear DNA sequences. Mol Phylogenet Evol 20:474-481 (2001).
Probatova NS, Sokolovskaya AP: Karyological study on vascular plants from the islands of the Far East state marine reserve [in Russian], in Chugunov YD (ed): Flowering Plants of the Islands of the Far East Marine Reserve, pp 92-114 (Far East Scientific Center of the USSR Academy of Sciences, Vladivostok 1981).
Ramsey J, Schemske DW: Pathways, mechanism, and rates of polyploid formation in flowering plants. Annu Rev Ecol Syst 29:467-501 (1998).
Rauscher JT, Doyle JJ, Brown AHD: Multiple origins and nrDNA internal transcribed spacer homeologue evolution in the Glycine tomentella (Leguminosae) allopolyploid complex. Genetics 166:987-998 (2004).
Romero Zarco C: Revisión taxonómica del género Avenula (Dumort.) Dumort. en la Península Ibérica e Islas Baleares. Lagascalia 13:39-146 (1984).
Romero Zarco C: Helictochloa Romero Zarco (Poaceae), a new genus of oat grass. Candollea 66:87-103 (2011).
Röser M: Karyologische, systematische und chorologische Untersuchungen an der Gattung Helictotrichon Besser ex Schultes & Schultes im westlichen Mittelmeergebiet. Diss Bot 145:1-250 (1989).
Röser M: Ecogeography of the grass genus Helictotrichon (Poaceae: Aveneae) in the Mediterranean and adjacent regions. Plant Syst Evol 203:181-281 (1996).
Röser M: Character evolution of the genus Helictotrichon (Poaceae: Aveneae) reconsidered in view of recent results in Ibero-Mauritanian and Eurasian species. Flora 193:425-447 (1998).
Röser M, Winterfeld G, Grebenstein B, Hemleben V: Molecular diversity and physical mapping of 5S rDNA in wild and cultivated oat grasses (Poaceae: Aveneae). Mol Phylogenet Evol 21:198-217 (2001).
Röser M, Döring E, Winterfeld G, Schneider J: Generic realignments in the grass tribe Aveneae (Poaceae). Schlechtendalia 19:27-38 (2009).
Sauer W: Die Gattung Avenula (Dumort.) Dumort. auf der Balkanhalbinsel. Acta Bot Croat 43:315-328 (1984).
Sauer W, Chmelitschek H: Beiträge zur Kenntnis ausdauernder Wildhafer: Die Gattung Avenula (Dumort.) Dumort. in den Ostalpen. Mitt Bot Staatssamml München 12:513-608 (1976).
Sauer W, Heubl GR: Beiträge zur Kenntnis ausdauernder Wildhafer: Karyotypanalysen an west- und osteuropäischen sowie an alpinen Wildhaferarten der Gattung Avenula (Dumort.) Dumort. (Poaceae). Phyton 24:193-223 (1984).
Schönswetter P, Stehlik I, Holderegger R, Tribsch A: Molecular evidence for glacial refugia of mountain plants in the European Alps. Mol Ecol 14:3547-3555 (2005).
Shaked H, Kashkush K, Ozkan H, Feldman M, Levy AA: Sequence elimination and cytosine methylation are rapid and reproducible responses of the genome to wide hybridization and allopolyploidy in wheat. Plant Cell 13:1749-1759 (2001).
Soltis DE, Soltis PS, Tate JA: Polyploidy: recurrent formation and genome evolution. Trends Ecol Evol 14:348-352 (1999).
Soltis DE, Soltis PS, Tate JA: Advances in the study of polyploidy since Plant speciation. New Phytol 161:173-191 (2004).
Soltis PS, Soltis DE: The role of genetic and genomic attributes in the success of polyploids. Proc Natl Acad Sci USA 97:7051-7057 (2000).
Song K, Lu P, Tang K, Osborn TC: Rapid genome change in synthetic polyploids of Brassica and its implications for polyploid evolution. Proc Natl Acad Sci USA 92:7719-7723 (1995).
Stebbins GL: Variation and Evolution in Plants (Columbia University Press, New York 1950).
Swofford DL: PAUP*: Phylogenetic Analysis Using Parsimony (*and Other Methods), vers. 4.0b10 (Sinauer Associates, Sunderland 2002).
Taketa S, Ando H, Takeda K, Von Bothmer R: Physical locations of 5S and 18S-25S rDNA in Asian and American diploid Hordeum species with the I genome. Heredity 86:522-530 (2001).
Taketa S, Ando H, Takeda K, Ichii M, Von Bothmer R: Ancestry of American polyploid Hordeum species with the I genome inferred from 5S and 18S-25S rDNA. Ann Bot 96:23-33 (2005).
Tayalé A, Parisod C: Natural pathways to polyploidy in plants and consequences for genome reorganization. Cytogenet Genome Res 140:79-96 (2013).
Thomas HM, Harper JA, Meredith MR, Morgan WG, Thomas ID, et al: Comparison of ribosomal DNA sites in Lolium species by fluorescence in situ hybridization. Chromosome Res 4:486-490 (1996).
Tzvelev NN: Zlaki SSSR [in Russian] (Nauka Publishers, Leningrad 1976).
Wang J, Lee JJ, Tian L, Lee HS, Chen M, et al: Methods for genome-wide analysis of gene expression changes in polyploids. Methods Enzymol 395:570-596 (2005).
Weiss-Schneeweiss H, Emadzade K, Jang TS, Schneeweiss GM: Evolutionary consequences, constraints and potential of polyploidy in plants. Cytogenet Genome Res 140:137-150 (2013).
Wendel JF: Genome evolution in polyploids. Plant Mol Biol 42:225-249 (2000).
Wendel JF, Schnabel A, Seelanan T: Bidirectional interlocus concerted evolution following allopolyploid speciation in cotton (Gossypium). Proc Natl Acad Sci USA 92:280-284 (1995).
Whittall J, Liston A, Gisler S, Meinke RJ: Detecting nucleotide additivity from direct sequences is a SNAP: an example from Sidalcea (Malvaceae). Plant Biol 2:211-217 (2000).
Winterfeld G: Molekular-cytogenetische Untersuchungen an Hafergräsern (Aveneae) und anderen Poaceae. Stapfia 86:1-170 (2006).
Winterfeld G, Röser M: Chromosomal localization and evolution of satellite DNAs and heterochromatin in grasses (Poaceae), especially tribe Aveneae. Plant Syst Evol 264:75-100 (2007).
Winterfeld G, Döring E, Röser M: Chromosome evolution in wild oat grasses (Aveneae) revealed by molecular phylogeny. Genome 52:361-380 (2009a).
Winterfeld G, Schneider J, Röser M: Allopolyploid origin of Mediterranean species in Helictotrichon (Poaceae) and its consequences for karyotype repatterning and homogenization of rDNA repeat units. Syst Biodivers 7:277-295 (2009b).
Winterfeld G, Perner K, Röser M: Genome composition and origin of the polyploid Aegean grass Avenula agropyroides (Poaceae). J Biogeogr 38:727-741 (2011).
Winterfeld G, Schneider J, Perner K, Röser M: Origin of highly polyploids: different pathways of auto- and allopolyploidy in 12-18x species of Avenula (Poaceae). Int J Plant Sci 173:1-14 (2012).
Wu Z, Phillips SM: Helictotrichon Besser ex Schultes & J.H. Schultes, in Wu ZY, Raven PH, Hong DY (eds): Flora of China, vol 22 (Poaceae), pp 317-322 (Science Press, Beijing 2006).
Zhang D, Sang T: Physical mapping of ribosomal RNA genes in peonies (Paeonia, Paeoniaceae) by fluorescent in situ hybridization: implications for phylogeny and concerted evolution. Am J Bot 86:735-740 (1999).
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