Chromosome numbers and karyotypes of 18 species of Epimedium sect. Diphyllon (Berberidaceae) from central China

Epimedium is the largest and one of the most important herbaceous genera in Berberidiaceae, especially for section Diphyllon, which has a diversification center in central China. Chromosome numbers and karyomorphology of 24 accessions were examined, representing 18 Epimedium species, five of which were counted here for the first time. A chromosome number of 2n = 2x = 12 was observed for all taxa and all karyotypes were Stebbins' 2A, except for E. acuminatum, E. brevicornu, E. ilicifolium and one accession of E. leptorrhizum, which were 3A. Their asymmetry index (AI) values vary from 1.71 to 4.56. Intercalary satellites are commonly found on the first or second pair. More than two individuals were sampled for E. franchetii, E. leptorrhizum, E. stellulatum, and E. wushanense and all had consistent and stable cytological traits with respect to their karyotype formula, Stebbins' asymmetry, and Al values, except for E. leptorrhizum. The significance and limits of the cytological results for Epimedium are also briefly discussed.