Chromosome number variation in the polyploid Cerastium alpinum‐C. arcticum complex (Caryophyllaceae)

Chromosome numbers of Cerastium alpinum, C. arcticum , and C. nigrescens were studied from the main part of their distribution area. No chromosome number variation was found within C. alpinum , which seems to be octoploid throughout its range. Dodecaploid chromosome numbers (2n = 108) were found in both C. arcticum and C. nigrescens. A higher, possibly aneuploid, chromosome number was reported for plants from Southwest Greenland, and the intermediate chromosome number of 2n = 90 was found in potential hybrids between C. alpinum and C. nigrescens. Despite sporadic reports of deviating chromosome numbers, the chromosome number variation within the C. alpinum‐C. arcticum complex seems to be restricted mainly to the octo‐ and dodecaploid levels.