Chromosome numbers, karyotypes and nuclear DNA contents from perennial polyploid groups of Cerastium (Caryophyllaceae)

Somatic chromosome numbers have been determined for the following Cerastium taxa: C. eriophorum (2n = 36), C. alpinum (2n = 72), C. transsylvanicum (2n = 108), C. arcticum (2n = 108), C. latifolium (2n = 36), C. carinthiacum (2n = 36), C. banaticum (2n = 36), C. arvense subsp. glandulosum (2n = 36), C. arvense subsp. arvense (2n = 72) and C. fontanum (2n = 144). Karyotypes of three diploid species (C. eriophorum, C. banaticum and C. latifolium), belonging to three different taxonomic groups, were analysed and found to be similar. The relative nuclear DNA contents of all taxa were determined by flow cytometry and, for five species, also by Feulgen cytophotometry. The values obtained by the two methods are similar. A comparison of nuclear DNA contents among diploids shows that values differ significantly between different taxonomic groups, and are correlated with average chromosome size. Within closely related polyploid groups nuclear DNA amounts increase from 2x- to 4x- and 6x taxa as 1 : 1.4 : 2.4 in the C. alpinum complex, whereas DNA amounts are doubled comparing 2x- and 4x-subspecies in the C. arvense complex.