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 (2 n;= 108), C. arcticum (2n = 108), C. latifolium (2n = 36), C. carinthiacum (2n = 36), C. bunaticum (2n = 36), (C. arvense subsp. glandulosum (2n = 36) , C. arvense subsp. arvense (2n = 72) and C. fontanum (2n = 144). Karyotype s of three diploid species (C. eriophorum, C. bunaticum and C latifolium), belonging to three different taxonomic groups, were analysed and found to b e 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 dif ferent taxonomic groups, and are correlated with average chromosome size. W ithin 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 DN A amounts are doubled comparing 2x- and 4x-subspecies in the C. arvense com plex.