Chloroplast DNA phylogeography of Photinia glabra (Rosaceae) in Japan.

Climate changes during glacial periods have had significant effects on the present geographic distribution of plant species. To elucidate the evolutionary history of a plant species with a disjunctive distribution, we investigated the geographic distribution patterns of cpDNA haplotypes in Photinia glabra (Rosaceae) growing in broadleaved evergreen forests in Japan. We examined cpDNA in 42 populations of P. glabra sampled over a geographic range that included Kinki and its surrounding areas and the disjunctive regions in the Amakusa Islands. Both areas had unique cpDNA haplotypes. Moreover, the AMOVA revealed that a large proportion of the total variance (51%, P < 0.001) could be explained by differences among these regions. These results suggest a past fragmentation of this plant species into two separate refugia: southwestern Kyushu and Kinki, including the surrounding area, during the Quaternary glacial periods. A particularly interesting result was that in the southern disjunct distribution in the Amakusa Islands, the genetic subdivision (Φ(CT) = 1.00, P < 0.001) appears to lie between the populations from nearly contiguous islands located across a fairway only approximately 80 to 150 m in width.