Extremely low levels of genetic variation in the critically endangered monotypic fern genus Mankyua chejuense (Ophioglossaceae) from Korea: Implications for conservation

► Genetic diversity was extremely low in the rare monotypic fern Mankyua chejuense. ► High degree of population differentiation was found in M. chejuense. ► Homozygous genotypes for alternative alleles at a few loci were detected. ► This result suggests occurrence of intragametophytic self-fertilization. ► In situ protection of habitats of standing populations is needed.