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Cytotype diversity and genome size variation in Knautia (Caprifoliaceae, Dipsacoideae).

Frajman B, Rešetnik I, Weiss-Schneeweiss H, Ehrendorfer F, Schönswetter P - BMC Evol. Biol. (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Institute of Botany, University of Innsbruck, Sternwartestraße 15, A-6020, Innsbruck, Austria.

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.

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Related in: MedlinePlus

Flow cytometry histograms showing genuine differences in relative genome size. Histograms showing differences within ploidy levels of Knautia (a–b) and the divergent relative genome size of the Iberian taxa, exemplified by tetra- and hexaploid K. rupicola (d). a diploid Knautia drymeia (K040, right) and K. lebrunii (K408, left). b Tetraploid K. nevadensis (K405, right, and K406, left). c Hexaploid K. dipsacifolia (K029, right, and K038, left). d From left to right: diploid K. drymeia (K039), tetraploid K. dinarica (K028) and K. rupicola (K400), hexaploid K. ressmannii (K449) and K. rupicola (K402)
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Fig4: Flow cytometry histograms showing genuine differences in relative genome size. Histograms showing differences within ploidy levels of Knautia (a–b) and the divergent relative genome size of the Iberian taxa, exemplified by tetra- and hexaploid K. rupicola (d). a diploid Knautia drymeia (K040, right) and K. lebrunii (K408, left). b Tetraploid K. nevadensis (K405, right, and K406, left). c Hexaploid K. dipsacifolia (K029, right, and K038, left). d From left to right: diploid K. drymeia (K039), tetraploid K. dinarica (K028) and K. rupicola (K400), hexaploid K. ressmannii (K449) and K. rupicola (K402)

Mentions: Forty-two out of 54 analysed taxa (77.8 %) possessed only one ploidy level, of which 57.1 % were diploids, 38.1 % tetraploids and 4.8 % hexaploids. Ten taxa (18.5 %) had two ploidy levels, of these 70 % were di-/tetraploids and 30 % tetra-/hexaploids. Two taxa (3.7 %), i.e. K. illyrica and K. travnicensis, contained all three ploidy levels. The mean RGS differed significantly between any two ploidy levels (Kruskal-Wallis test followed by Mann–Whitney pairwise comparison and Bonferroni corrections of p values; Fig. 3). Diploid populations also differed significantly from tetraploids and hexaploids in monoploid RGS, whereas there was no significant difference between tetraploids and hexaploids (Fig. 3). The same results were obtained after the exclusion of the Iberian taxa K. legionensis, K. nevadensis, K. rupicola and K. subscaposa with clearly higher monoploid RGS. Intra-ploidy variation in RGS was relatively large in all three ploidy levels in section Trichera (1.69-fold variation in diploids, 1.57-fold variation in tetraploids, 1.40-fold variation in hexaploids). The highest intraspecific RGS variation within a ploidy level was observed in K. integrifolia from sect. Tricheroides (1.60-fold variation); in sect. Trichera the highest variation was in diploid K. drymeia (1.21-fold variation). Intraspecific intra-cytotype variation was confirmed with simultaneous analyses of samples with different RGS, yielding histograms with one bifurcate (Fig. 4a) or two separate peaks (Figs. 4b, 4c).Fig. 3


Cytotype diversity and genome size variation in Knautia (Caprifoliaceae, Dipsacoideae).

Frajman B, Rešetnik I, Weiss-Schneeweiss H, Ehrendorfer F, Schönswetter P - BMC Evol. Biol. (2015)

Flow cytometry histograms showing genuine differences in relative genome size. Histograms showing differences within ploidy levels of Knautia (a–b) and the divergent relative genome size of the Iberian taxa, exemplified by tetra- and hexaploid K. rupicola (d). a diploid Knautia drymeia (K040, right) and K. lebrunii (K408, left). b Tetraploid K. nevadensis (K405, right, and K406, left). c Hexaploid K. dipsacifolia (K029, right, and K038, left). d From left to right: diploid K. drymeia (K039), tetraploid K. dinarica (K028) and K. rupicola (K400), hexaploid K. ressmannii (K449) and K. rupicola (K402)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4504173&req=5

Fig4: Flow cytometry histograms showing genuine differences in relative genome size. Histograms showing differences within ploidy levels of Knautia (a–b) and the divergent relative genome size of the Iberian taxa, exemplified by tetra- and hexaploid K. rupicola (d). a diploid Knautia drymeia (K040, right) and K. lebrunii (K408, left). b Tetraploid K. nevadensis (K405, right, and K406, left). c Hexaploid K. dipsacifolia (K029, right, and K038, left). d From left to right: diploid K. drymeia (K039), tetraploid K. dinarica (K028) and K. rupicola (K400), hexaploid K. ressmannii (K449) and K. rupicola (K402)
Mentions: Forty-two out of 54 analysed taxa (77.8 %) possessed only one ploidy level, of which 57.1 % were diploids, 38.1 % tetraploids and 4.8 % hexaploids. Ten taxa (18.5 %) had two ploidy levels, of these 70 % were di-/tetraploids and 30 % tetra-/hexaploids. Two taxa (3.7 %), i.e. K. illyrica and K. travnicensis, contained all three ploidy levels. The mean RGS differed significantly between any two ploidy levels (Kruskal-Wallis test followed by Mann–Whitney pairwise comparison and Bonferroni corrections of p values; Fig. 3). Diploid populations also differed significantly from tetraploids and hexaploids in monoploid RGS, whereas there was no significant difference between tetraploids and hexaploids (Fig. 3). The same results were obtained after the exclusion of the Iberian taxa K. legionensis, K. nevadensis, K. rupicola and K. subscaposa with clearly higher monoploid RGS. Intra-ploidy variation in RGS was relatively large in all three ploidy levels in section Trichera (1.69-fold variation in diploids, 1.57-fold variation in tetraploids, 1.40-fold variation in hexaploids). The highest intraspecific RGS variation within a ploidy level was observed in K. integrifolia from sect. Tricheroides (1.60-fold variation); in sect. Trichera the highest variation was in diploid K. drymeia (1.21-fold variation). Intraspecific intra-cytotype variation was confirmed with simultaneous analyses of samples with different RGS, yielding histograms with one bifurcate (Fig. 4a) or two separate peaks (Figs. 4b, 4c).Fig. 3

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Institute of Botany, University of Innsbruck, Sternwartestraße 15, A-6020, Innsbruck, Austria.

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.

Show MeSH
Related in: MedlinePlus