Low within population genetic variation and high among population differentiation in cyrtomium falcatum (L.f.) C. Presl (Dryopteridaceae) in southern korea: Inference of population-establishment history

In the Korean Peninsula, the current distribution of the warm-temperate and subtropical vegetation (including many homosporous ferns) is limited to southern coastal areas. Paleoecological data suggest that during the Last Glacial Maximum this vegetation retreated to glacial refugia putatively located in southern Japan and/or southern China, followed by a post-glacial recolonization. Two broad scenarios of post-glacial recolonization could be hypothesized: extant Korean populations are derived from multiple source populations (i.e., from multiple refugia); alternatively, they originate from a single refugium. To test which of these scenarios is more likely, we surveyed patterns of genetic diversity in eight (n=307) populations of Cyrtomium falcatum from southern Korea. We found extremely low levels of allozyme variation within populations coupled with high among-population differentiation. These data best support the second hypothesis, and indicate that the current genetic diversity may be a consequence of post-glacial long-distance dispersal events and subsequent founder effects. In addition, restricted gene flow among the discontinuous populations of C. falcatum in southern Korea has likely contributed to the high degree of among-population genetic differentiation. From a conservation perspective, several populations should be targeted for both in situ and ex situ conservation, as C. falcatum exhibits a high degree of divergence among populations.