The Cerastium alpinum-C. arcticum complex (Caryophyllaceae):: numerical analyses of morphological variation and a taxonomic revision of C. arcticum Lange s.l.

Morphological variation of Cerastium alpinum L., C. arcticum Lange, and related taxa was investigated by numerical analyses. The analyses showed that the present division into two species is inappropriate and does not cover the levels of variation within the C. alpinum-C. arcticum complex. Two alternative models for a new and functional taxonomy of the complex are discussed: (1) that there is one widely defined species, C. alpinum. including several subspecies, (2) alternatively that arctic and non-arctic populations of what currently is named C. arcticum belong to two different taxa, both distinct from C. alpinum. Our studies indicate the presence of several evolutionary lineages, which are not adequately accounted for by the recognition of a widely circumscribed C. alpinum, and support a subdivision of current C. arcticum into two separate species, C, arcticum Lange s.str. and C. nigrescens (H.C. Watson) Edmondston ex H.C. Watson. A revised taxonomic treatment is presented.