Notes on genetic variation in Sedum sarmentosum (Crassulaceae): Implications for the origin of southern Korean populations

Abstract

An area comprising Juwangsan National Park and its adjacent mountains (southeastern Korean Peninsula) is a good model system for testing the effects of physical barriers to gene flows in plant populations. We predicted that plant species consisting of isolated populations are genetically more differentiated than those that are rather continuously distributed. Most populations of Sedum polytrichoides occur in four isolated valleys, and we assessed the genetic variability and structures using twelve allozyme loci in ten populations. We also compared the present results to earlier findings pertaining to the two co-occurring herbs Hylotelephium ussuriense (≡ Sedum ussuriense) (growing only in the four isolated valleys) and S. kamtschaticum (rather continuously distributed). We found moderate levels of within-population genetic variation in S. polytrichoides (H e = 0.112). Estimates of among-population divergence in S. polytrichoides were also moderate (F S T = 0.250) and, as expected, very similar to that of H. ussuriense (0.261) but considerably higher than the variation in S. kamtschaticum (0.165). An analysis of molecular variance (AMOVA) revealed that S. polytrichoides and H. ussuriense had higher percentages of among-valley variation (19% each) than S. kamtschaticum (4%). Most of this variation, as also indicated by the STRUCTURE program, was due to differences in genetic profiles between the two central valleys. We concluded that the genetic differences observed between species (S. kamtschaticum vs. S. polytrichoides and H. ussuriense) are mainly due to differences in their distribution within the study area.