Abstract
Southern rear edge populations of cold-adapted plants at low latitudinal margins will probably be critical for determining species' responses to climate change. We focused on southern rear edge populations of an arctic-alpine plant, Dryas octopetala, in the high mountains of the Far East to assess genetic diversity and genetic structure by using allozyme variation and chloroplast DNA sequences. Allozyme data revealed low genetic diversity within populations (H_e = 0.003-0.144), but high genetic differentiation among populations (G_<ST> = 0.403), indicating characteristics of small and isolated populations that have persisted on mountain sky islands. The loss of genetic diversity was particularly pronounced in central Japan. On the basis of the cpDNA-haplotype distribution, the distinctive relationship between central Japan and not only northern Japan but also parts of Eurasia suggests that southernmost populations in the high mountains of central Japan are long-standing relicts of the Quaternary climate oscillations. Their refugial history therefore shaped the genetic diversity and genetic structure of the southern rear edge populations in Far East Asia.
