Origin of Highly Polyploid Species: Different Pathways of Auto- and Allopolyploidy in 12–18x Species ofAvenula(Poaceae)

Abstract

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Polyploidy and Hybridization as Main Factors of Speciation: Complex Reticulate Evolution within the Grass Genus <b><i>Helictochloa</i></b>

“…A comparison between the M and V genome allopolyploids H. adsurgens and H. cincinnata suggests that parental M genome ITS rDNA sequences have persisted in the former polyploid with fewer changes than in the latter. As found already in other species [Winterfeld et al, 2012], different ITS rDNA variants (original and recombinant) appear to survive after hybridization and polyploidization in allopolyploids of higher valence much better than in taxa with low ploidal level. Due to the initially higher number of rDNA loci in the former, a generally slower rate of sequence homogenization or interlocus gene conversion mechanisms can be inferred with some plausibility.…”

“…Two types of ITS rDNA sequences found among the diploid taxa correlated with special chromosomal features and different geographical distribution of these species [Winterfeld et al, 2011]. Studies on the mechanisms of allo-versus autopolyploid speciation in 3 natural polyploids of Helictochloa (12x-18x) from SE Europe and Asia Minor revealed a pronounced capability of highly polyploids to incorporate seemingly rather easily further genomes via hybridization or introgression [Winterfeld et al, 2012].…”

“…Taketa et al, 2005;Badaeva et al, 2010b]. Comparisons between the molecular data, the results from previous cytogenetic and karyotype studies [Winterfeld, 2006;Winterfeld et al, 2009aWinterfeld et al, , b, 2011Winterfeld et al, , 2012 and the taxonomical treatment of this group, which is based mainly on morphological and anatomical features [e.g. Holub, 1958[e.g.…”

“…According to morphological, karyological and chorological data, it was suggested that the genus consists of ∼ 6-7 separate species complexes which have evolved independently in parallel and accompanied by polyploidy. Chromosome numbers range from 2n = 2x = 14 up to 2n = 22x = 154 [Gervais, 1973;Romero Zarco, 1984;Sauer, 1984;Röser, 1996Röser, , 1998Winterfeld, 2006;Winterfeld et al, 2009aWinterfeld et al, , b, 2011Winterfeld et al, , 2012.…”

“…Doyle et al, 2000;Popp and Oxelman, 2001;Petersen et al, 2006;Fortune et al, 2008], additive polymorphic sites detected in the internal transcribed spacer (ITS) region [cf. Baldwin et al, 1995;Campbell et al, 1997;Whittall et al, 2000] or plasmid-cloned individual copies [Blattner, 2004;Winterfeld et al, 2009bWinterfeld et al, , 2011Winterfeld et al, , 2012Peng et al, 2010]. However, none of the species complexes distinguished within Helictochloa could be resolved in the molecular phylogenetic studies conducted so far.…”