Contrasting levels of clonal and within-population genetic diversity between the 2 ecologically different herbs Polygonatum stenophyllum and Polygonatum inflatum (Liliaceae)

Comparative studies on clonal and genetic structure between ecologically contrasting congeners may provide valuable insights into the mechanisms promoting the maintenance of genetic diversity in clonal plant species. Polygonatum stenophyllum has long rhizomes (ca. 30-40 cm long) and largely occurs on sandy soils in open river banks, whereas its congener Polygonatum inflatum has short ones (ca. 5-10 cm long) and occurs on humic soils under deciduous forests. Using 21 allozyme loci, we comparatively assessed levels of clonal and genetic diversity in the 2 clonal species. Seven populations of P. stenophyllum consisted of single clones, and levels of within-population clonal and genetic variation were considerably lower than those of P. inflatum. However, when samples were pooled, P. stenophyllum harbored higher genetic variation than P. inflatum, which is due to higher among-population genetic differentiation in the former species compared with the latter (F_ST = 0.636 vs. F_ST = 0.165). Our data suggest that populations of P. stenophyllum have been mainly founded by a single seed or rhizome (through river water) or by a few seeds, whereas populations of P. inflatum would have been established through multiple, repeated seedling recruitment. Moderate levels of genetic diversity in a population of P. stenophyllum located at the foot of the Baekdudaegan Mountains and in all the populations of P. inflatum are consistent with the previous hypothesis that these mountains served as a glacial refugium for many boreal species of the Korean Peninsula.