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We studied the relationship between genome size and ploidy level variation and plant traits for the reed grass Phragmites australis. Using a common garden approach on a global collection of populations in Aarhus, Denmark, we investigated the influence of monoploid genome size and ploidy level on the expression of P. australis growth, nutrition and herbivore-defense traits and whether monoploid genome size and ploidy level play different roles in plant trait expression. We found that both monoploid genome size and latitude of origin contributed to variation in traits that we studied for P. australis, with latitude of origin being generally a better predictor of trait values and that ploidy level and its interaction with monoploid genome size and latitude of origin also contributed to trait variation. We also found that for four traits, tetraploids and octoploids had different relationships with the monoploid genome size. While for tetraploids stem height and leaf water content showed a positive relationship with monoploid genome size, octoploids had a negative relationship with monoploid genome size for stem height and no relationship for leaf water content. As genome size within octoploids increased, the number of aphids colonizing leaves decreased, whereas for tetraploids there was a quadratic, though non-significant, relationship. Generally we found that tetraploids were taller, chemically better defended, had a greater number of stems, higher leaf water content, and supported more aphids than octoploids. Our results suggest trade-offs among plant traits mediated by genome size and ploidy with respect to fitness and defense. We also found that the latitude of plant origin is a significant determinant of trait expression suggesting local adaptation. Global climate change may favor some genome size and ploidy variants that can tolerate stressful environments due to greater phenotypic plasticity and to fitness traits that vary with cytotype which may lead to changes in population genome sizes and/or ploidy structure, particularly at species' range limits. [ABSTRACT FROM AUTHOR]

Due to its instantaneous effects on the genetics, phenotype, physiology and/or ecology of a plant, polyploidy can play an important role in facilitating plant invasions. Understanding the determinants of invasiveness in species with multiple ploidy levels requires a detailed knowledge of ploidy composition in native versus invaded ranges. Using DNA flow cytometry, we performed representative ploidy screening (277 localities, 333 individuals) across the native range of Oxalis pes- caprae and compared the data with those from invaded ranges. Both ranges showed striking differences in ploidy composition: whereas tetra- and especially pentaploids successfully colonized secondary areas, only di-, (very rare) tri- and tetraploids (dominant) were found in the native range of this species. Disregarding the diploid var. sericea, diploids and tetraploids of the nominate variety showed largely parapatric distribution in the native range, with a zone of overlap in the Northern Cape Province. Our results challenge the conventional scenario of the introduction of pentaploid individuals from the Greater Cape Floristic Region. The origin of the pentaploid cytotype is unclear and molecular tools applied in a large scale screening are needed to understand the invasion history of the species. [ABSTRACT FROM AUTHOR]

Flow cytometry (FCM) has been widely used in plant science to determine the amount of nuclear DNA, either in absolute units or in relative terms, as an indicator of ploidy. The requirement for fresh material in some applications, however, limits the value of FCM in field research, including plant biosystematics, ecology and population biology. Dried plant samples have proven to be a suitable alternative in some cases (large-scale ploidy screening) although tissue dehydration is often associated with a decrease in the quality of FCM analysis. The present study tested, using time-scale laboratory and in situ field experiments, the applicability of glycerol-treated nuclear suspension for DNA flow cytometry. We demonstrate that plant nuclei preserved in ice-cold buffer + glycerol solution remain intact for at least a few weeks and provide estimates of nuclear DNA content that are highly comparable and of similar quality to those obtained from fresh tissue. The protocol is compatible with both DAPI and propidium iodide staining, and allows not only the determination of ploidy level but also genome size in absolute units. Despite its higher laboriousness, glycerol-preserved nuclei apparently represent the most reliable way of sample preservation for genome size research. We assume that the protocol will provide a vital alternative to other preservation methods, especially when stringent criteria on the quality of FCM analysis are required. [ABSTRACT FROM AUTHOR]

Serpentine soils represent a unique environment that imposes multiple stresses on vegetation (low Ca/Mg ratios, macronutrient deficiencies, elevated heavy metal concentrations and drought). Under these conditions, a substantial role of arbuscular mycorrhizal (AM) symbiosis can be anticipated due to its importance for plant nutrition and stress alleviation. We tested whether serpentine and non-serpentine populations of Knautia arvensis (Dipsacaceae) differ in the benefits derived from native AM fungal communities. Four serpentine and four non-serpentine populations were characterised in terms of mycorrhizal colonisation and soil characteristics. The serpentine populations showed significantly lower mycorrhizal colonisation than their non-serpentine counterparts. The mycorrhizal colonisation positively correlated with soil pH, Ca and K concentrations and Ca/Mg ratio. Seedlings from each population were then grown for 3 months in their sterilised native substrates, either uninoculated or reinoculated with native AM fungi. Two serpentine and two non-serpentine populations responded positively to mycorrhizal inoculation, while no significant change in plant growth was observed in the remaining populations. Contrary to our hypothesis, serpentine populations of K. arvensis did not show higher mycorrhizal growth dependence than non-serpentine populations when grown in their native soils and inoculated with native AM fungi. [ABSTRACT FROM AUTHOR]

We explored the fine-scale distribution of cytotypes of the mountain plant Senecio carniolicus along an altitudinal transect in the Eastern Alps. Cytotypes showed a statistically significant altitudinal segregation with diploids exclusively found in the upper part of the transect, whereas diploids and hexaploids co-occurred in the lower range. Analysis of accompanying plant assemblages revealed significant differences between cytotypes along the entire transect but not within the lower part only, where both cytotypes co-occur. This suggests the presence of ecological differentiation between cytotypes with the diploid possessing the broader ecological niche. No tetraploids were detected, indicating the presence of strong crossing barriers. [ABSTRACT FROM AUTHOR]

Major demographic processes in Spartocytisus supranubius, an endemic shrub dominant in the alpine zone of Tenerife, Canary Islands, were studied by a combination of dendrochronological and demographical techniques. Dendrochronological data were used to estimate growth rates of adult shrubs, frequency of fragmentation of shrubs by clonal growth, mortality, and seedling establishment. Isozymes were used to identify the extent of clonal growth in the species. The data collected were used to construct population projection matrices and to identify the role of generative reproduction vs. clonal growth in the life cycle of the species. Both isozymes and morphological analysis showed that the shrub is capable of clonal growth, but its contribution to the variation in the growth rate is much smaller than that of generative reproduction. The current population dynamics of the shrub seem to be strongly affected by rabbit grazing of seedlings, which controls effective establishment of young shrubs. Analysis of data from enclosures shows that rabbit removal would lead to rapid population growth of the species. Transition matrices showed that Spartocytisus supranubius populations currently are likely decreasing; this contrasts with the rapid increase over the past 40 years shown by historical aerial photographs. The stage structure of the shrub is far from equilibrium, indicating that the dynamics are driven by rare establishment events; dendrochronological analysis identified a peak in regeneration around 1980; this can be attributes to a combination of cessation of management in the caldera and to a series of wet years in that period. [ABSTRACT FROM AUTHOR]

Flow cytometric and karyological investigations were performed on the closely related taxa Elytrigia repens and E. intermedia (Poaceae: Triticeae) from the Czech Republic. DNA-hexaploids clearly prevailed among 238 examined plants and amounted to 96.2% of all samples. 2C-values ± s.d. for hexaploid Elytrigia repens and E. intermedia were estimated at 23.27 ± 0.20 pg and 27.04 ± 0.24 pg respectively. Genome size thus allowed reliable separation of the two species (difference ca. 16%) as well as the identification of hybrid individuals. Natural hybridization in E. repens - E. intermedia alliance seems to be quite a common phenomenon as indicated from a large proportion (one sixth) of hexaploid samples with intermediate 2C-values. Previously, the crosses were most probably overlooked or misidentified due to their weak morphological differentiation. New nonaploid cytotypes (2n=9x=63) were revealed for both species as well as for the hybrid (determined on the basis of morphological characters only), representing the first records from the field. Fusion of unreduced and reduced gametes of the hexaploids is the most plausible mode of nonaploid origin. [ABSTRACT FROM AUTHOR]

Ploidy levels in Empetrum (crowberry) from the Czech Republic and from one adjacent locality in Poland were estimated by flow cytometry to examine cytotype distribution patterns at large (within the country), medium (within mountain ranges) and small (within particular localities) spatial scales. Diploid, triploid, and tetraploid individuals were found. Triploids are reported from Central Europe for the first time; they occurred in the Krkonoše Mts. Exclusively diploid plants were observed in three mountain ranges (the Krušné hory Mts., Labské pískovce Mts., Adršpašsko-Teplické skály Mts.), exclusively tetraploids were observed in the Jeseníky Mts., and both cytotypes were observed in the Šumava Mts., Jizerské hory Mts. and Krkonoše Mts. Except for the latter mountain range, diploids and tetraploids were always found in different habitats. Spatial isolation is supposed to be the main barrier preventing cytotype mating. A mosaic-like sympatric occurrence of different cytotypes was demonstrated in the Krkonoše Mts., where peat bogs and rocky places were not spatially separated. Eight of 11 localities studied there were inhabited by diploids and tetraploids (five localities), diploids and triploids (one locality) or all three ploidy levels (two localities). Diploid and triploid plants occasionally intermingled at 0.3 x 0.3 m. Flower sex in crowberries was strongly associated with ploidy level: diploids usually had unisexual flowers, the tetraploids bore exclusively bisexual flowers. However, a few diploid plants with hermaphrodite flowers occurred in one population in the Krkonose Mts. [ABSTRACT FROM AUTHOR]