Intraspecific DNA content variability in Festuca pallens on different geographical scales and ploidy levels.

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.