Genetic diversity and structure of the endangered species Megaleranthis saniculifolia in Korea as revealed by allozyme and ISSR markers

The genetic diversity and structure of 12 populations of Megaleranthis saniculifolia, a rare endemic Korean plant, were analyzed using 14 allozyme loci coding 10 enzymes and 78 ISSR loci using seven primers. The genetic diversity of M. saniculifolia at the species level was similar to that observed in out-crossing and long-lived perennials, while at the population level, it was significantly low. The high F _IS value of many populations as well as homozygote excess occurred relatively evenly in many populations in relation to the Hardy-Weinberg expectation, suggesting that inbreeding was occurring within the M. saniculifolia populations. The degree of genetic differentiation based on the two markers was high, and there was no correlation between geographic and genetic distance. Bayesian cluster analysis did not reveal any remarkable geographic trends. Positive correlations were observed between genetic diversity (H _e and h) and population size. Therefore, low genetic diversity within the population and high population differentiation of M. saniculifolia were closely related to the influence of genetic drift, particularly in highly isolated populations. In addition, the fixation of the main alleles at several loci in the opposite direction provided good evidence for genetic drift. The genetic diversity of M. saniculifolia could be compromised if the distribution area or the size of the population were further reduced. In particular, the isolated populations that are fragmented within an area could be at high risk of extinction due to accelerated inbreeding or genetic drift. Considering this, a close monitoring of the population size and of the changes in the genetic structure must be performed. Some practical measures for genetic conservation are also proposed.