High genetic diversity in a threatened clonal species, Cypripedium calceolus (Orchidaceae), enables long-term stability of the species in different biogeographical regions in Estonia

In plants capable of clonal reproduction, demographic and ecological investigations are essential for understanding the factors contributing to population diversity. The perennial, clonal orchid Cypripedium calceolus has a variable status in Europe and Asia, being threatened with extinction in some countries and abundant in others. In Estonia, thriving populations can be observed in different biogeographical regions. The aim of this study was to characterize genetic diversity and differentiation in Estonian populations, by comparing the current variation with long-term observations of the clonal system and taking into account climatic variables. Diversity at 11 microsatellite loci for 11 populations representing the boreal and nemoral regions was investigated. Some signatures of bottleneck and recent founder events were detected, with a high genetic diversity in terms of heterozygosity and allele diversity and a pattern of differentiation not strictly correlated with geographical factors. Globally, information regarding population dynamics in C. calceolus provides the possibility to inform conservation management, prevent loss of ancestral variation and promote intra-population divergence through the combination of gene flow and ecological change related to the clonal system.