Phylogeography based on intraspecific sequence variation in chloroplast DNA ofMiscanthus sinensis(Poaceae), a native pioneer grass in Japan

Miscanthus sinensis Andersson is a dominant perennial grass in East Asia, where it is a pioneer species in disturbed habitats. To obtain basic information about the genetic structure of this pioneer species, we investigated chloroplast DNA (cpDNA) variation in M. sinensis within and among native populations across Japan. We detected nine haplotypes in 636 individuals from 30 populations. Two distinct haplotypes had a wide geographical distribution and coexisted within most of the populations. The degree of genetic differentiation among the populations was relatively low. Two putative ancestral lineages were distributed in the Ryukyu Islands. Therefore, it is possible that lineages that originated in subtropical areas of mainland China migrated into the Ryukyu Islands via Taiwan. Another possible migration route is the Korean Peninsula. Two major haplotypes may have migrated from the Eurasian continent to the northern coast in Kyushu via the Korean Peninsula and then expanded throughout Japan. There was no clear genetic boundary among the populations north of Kyushu. The enhanced immigration ability and high rate of gene flow of Miscanthus may have modulated the genetic structure created during previous glacial periods. Alternatively, the shortage of unique haplotypes north of Kyushu may indicate the recent expansion of this species to northern Japan.