Marked differences in genetic diversity and differentiation between the centre and edge of the geographical range of Megaleranthis saniculifolia (Ranunculaceae), a Korean endemic species

Abstract

The amount and distribution of genetic diversity within and between Megaleranthis saniculifolia Ohwi populations were compared between the central and peripheral regions of the species distribution. Allozyme and ISSR markers were used for genetic analysis of six populations from the central region (DY) and five populations from the peripheral region (MJ). Genetic diversity was substantially higher in the DY region than in the MJ region. Relatively uniform homozygote excess at many loci in most populations indicated that M. saniculifolia was influenced by a substantial degree of inbreeding in both regions. The degree of differentiation between populations was remarkably higher in the MJ region than in the DY region. Cluster analysis showed a trend towards separation between regions, although populations in the MJ region exhibited a slightly different trend according to the markers. We conclude that genetic drift has been affecting the populations in the MJ region for a long time, on the basis of their low genetic diversity, high differentiation, U-shaped allele-frequency distribution, and fixation of alleles towards opposing frequencies (1 or 0) among populations. In contrast, the DY region maintained relatively stable populations, although evidence of a recent bottleneck was found in one population. Along with some practical measures for genetic conservation, we present an optimal sample size for ex situ conservation to secure as many common alleles as possible.