Nejvíce citovaný článek - PubMed ID 15026300
Microgeographic genome size differentiation of the carob tree, Ceratonia siliqua, at 'Evolution Canyon', Israel
BACKGROUND AND AIMS: The spatial and statistical distribution of genome sizes and the adaptivity of genome size to some types of habitat, vegetation or microclimatic conditions were investigated in a tetraploid population of Festuca pallens. The population was previously documented to vary highly in genome size and is assumed as a model for the study of the initial stages of genome size differentiation. METHODS: Using DAPI flow cytometry, samples were measured repeatedly with diploid Festuca pallens as the internal standard. Altogether 172 plants from 57 plots (2.25 m(2)), distributed in contrasting habitats over the whole locality in South Moravia, Czech Republic, were sampled. The differences in DNA content were confirmed by the double peaks of simultaneously measured samples. KEY RESULTS: At maximum, a 1.115-fold difference in genome size was observed. The statistical distribution of genome sizes was found to be continuous and best fits the extreme (Gumbel) distribution with rare occurrences of extremely large genomes (positive-skewed), as it is similar for the log-normal distribution of the whole Angiosperms. Even plants from the same plot frequently varied considerably in genome size and the spatial distribution of genome sizes was generally random and unautocorrelated (P > 0.05). The observed spatial pattern and the overall lack of correlations of genome size with recognized vegetation types or microclimatic conditions indicate the absence of ecological adaptivity of genome size in the studied population. CONCLUSIONS: These experimental data on intraspecific genome size variability in Festuca pallens argue for the absence of natural selection and the selective non-significance of genome size in the initial stages of genome size differentiation, and corroborate the current hypothetical model of genome size evolution in Angiosperms (Bennetzen et al., 2005, Annals of Botany 95: 127-132).
BACKGROUND AND AIMS: Intraspecific genome size variability of Festuca pallens occurring on relict rocky steppes in Central Europe was studied on two ploidy levels and three geographical scales: (1) local scale of 24 populations, (2) landscape scale of three transects in river canyons or hill systems, and (3) global scale of 160 samples covering the whole distribution area. METHODS: DAPI flow cytometry of homogeneously cultivated samples (>or=1 year), measured randomly with two internal standards, Lycopersicon esculentum and Pisum sativum. Differences in DNA content were confirmed (1) by the double peaks of simultaneously measured samples, (2) based on measurements carried out in different seasons, and (3) by additional measurements with propidium iodide. KEY RESULTS: On a global scale, the relative DNA content ranged between 1.170-fold in diploids and 1.164-fold in tetraploids. A maximum difference of 1.088-fold between the mean relative DNA content of nearby populations was found. In 16 of 24 populations significant variability was shown (P<0.001, 1.121-fold as maximum). For both ploidy levels, the relative genome size had the same range and geographical pattern, correlated with geographical coordinates (P<0.01). Diploids with larger genomes occur on relict habitats (P<0.01), and in areas of periglacial steppes (20,000 years ago; P<0.02). In tetraploids, the relative DNA content differs among the three previously recognized geographical types (Alpine, Pannonian and Scabrifolia, P<0.001). Tetraploids have a relative DNA content smaller than twice that of the diploids (P<0.001). An influence of microhabitat on DNA content variation was not confirmed. CONCLUSIONS: Genome size variability occurs over all spatial scales: intrapopulation, landscape and global. Correlation between geographical coordinates and palaeovegetation type, concomitant with diploids and tetraploids, and no influence of microhabitat were found. Genome size decreases in tetraploids. Lower CVs, and thus higher accuracy, resolution and reproducibility, favour DAPI measurements for the study of intraspecific genome size variability.
- MeSH
- DNA rostlinná analýza MeSH
- ekosystém * MeSH
- Festuca genetika MeSH
- genetická variace MeSH
- genom rostlinný MeSH
- indoly MeSH
- ploidie * MeSH
- průtoková cytometrie MeSH
- zeměpis MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Evropa MeSH
- Názvy látek
- DAPI MeSH Prohlížeč
- DNA rostlinná MeSH
- indoly MeSH
