Environmental factors contribute to the formation and maintenance of the contact zone observed in deciduous broad-leaved tree species in Japan.

Contact zones are defined as areas where populations from different refugia meet during a postglacial expansion and distinct DNA lineages are mixedly distributed. In Japan, contact zones of various plants and animals were reported from the Kinki-Chugoku region. These contact zones appear to be maintained without any drastic topographic barriers such as those observed in the Alps and Pyrenees Mountains.

Comparative phylogeography of four component species of deciduous broad-leaved forests in Japan based on chloroplast DNA variation.

A phylogeographic study of four tree species (Padus grayana, Euonymus oxyphyllus, Magnolia hypoleuca, and Carpinus laxiflora) growing in Japanese deciduous broad-leaved forests was conducted based on chloroplast DNA (cpDNA) variations. Using nucleotide sequences of 702-1,059 bp of intergenic spacers of cpDNA, 20, 27, eight, and eight haplotypes were detected among 251, 251, 226, and 262 individuals sampled from 67, 79, 75, and 71 populations of the above species, respectively. The geographical pattern of the cpDNA variations was highly structured in each species, and the following three regional populations were genetically highly differentiated among all four species: (1) the Sea of Japan-side area, (2) the Kanto region, and (3) southwestern Japan.

Genetic structure of an endemic Japanese conifer, Sciadopitys verticillata (Sciadopityaceae), by using microsatellite markers.

We investigated the genetic structure of Sciadopitys verticillata, an endemic conifer in Japan, using 11 microsatellite markers. Average expected heterozygosity varied from 0.282 to 0.

Intraspecific sequence variation of chloroplast DNA among the component species of deciduous broad-leaved forests in Japan.

To select appropriate plant materials for a phylogeography of deciduous broad-leaved forests in Japan, we surveyed intraspecific chloroplast DNA variation in 34 species found in these forests. A relatively large number of intraspecific cpDNA variations were detected in ten species: Carpinus japonica (nucleotide diversity pi=0.00083), C.