Cytological study of a fern Cystopteris fragilis in Mongolian Altai

Cystopteris fragilis collected in Mongolian Altai showed three cytotypes with chromosome numbers of tetraploid (2n=c.168), pentaploid (2n=c.210) and hexaploid (2n=c.252). Flow cytometry analysis also showed three different peaks of DNA contents of nuclei in fronds. Meiotic metaphase chromosomes of the spore mother cells in the tetraploid and hexaploid C. fragilis showed all bivalents with c.84II and c.126II, while those of the pentaploid C. fragilis showed many univalents and bivalents that produced mostly sterile spores. The pentaploid C. fragilis was suggested to be a hybrid between the tetraploid and the hexaploid C. fragilis.