Genetic diversity of a relict plant species, Ligularia sibirica (L.) Cass. (Asteraceae)

Rare plant species can be divided into naturally, ‘old rare’ species and anthropogenically, ‘new rare’ species. Many recent studies explored genetic diversity of ‘new rare’ species. Less is, however, known about genetic diversity of ‘old rare’ species. We examined isozyme genetic variability of 20 populations of an ‘old rare’ plant species, Ligularia sibirica (Asteraceae) in the Czech and Slovak Republic. It is a long-lived perennial herb with mixed-mating breeding system, widely distributed from East Asia to European Russia, with few isolated relict populations in the remaining part of Europe.The results showed high genetic diversity within populations (80.8%) and a low level of genetic differentiation (FST = 0.179). Genetic distance between populations correlated significantly with geographic distance. There was also a significant positive correlation between genetic diversity and population size. This is probably caused by destruction of habitats in last centuries and subsequent decrease of population size. Patterns of genetic diversity suggest that the recent distribution is a result of stepwise postglacial migration of the species and subsequent natural fragmentation.We conclude that L. sibirica populations preserve high levels of genetic diversity and are not yet threatened by genetic factors. However, this may change if changes in habitat conditions continue.