MITOCHONDRIAL-DNA VARIATION FOLLOWS A GEOGRAPHIC PATTERN IN JAPANESE BEECH SPECIES

The amount and distribution of mitochondrial (mt) DNA restriction frag ment length polymorphism was determined among individual tree samples of two Japanese beech species, Fagus crenata and F.japonica. Individua l plants were collected from 16 F.crenata populations throughout the r ange of the species, and from three F.japonica populations. We detecte d enough variation to characterize eleven and three chondriome types i n F.crenata and F.japonica, respectively. The grouping of beech chondr iome types based upon the cladistic analysis of mtDNA polymorphism all owed us to recognize the apparent geographical patterns of mtDNA diver sity: the resulting three main groups occupied distinct geographic are as. This geographic differentiation is likely to reflect the history o f the Japanese beech forests after the last glacial period of the Plei stocene. In addition, the mtDNA polymorphism encountered within F.cren ata encompassed all the variation observed in F.japonica. Our result s uggests the need for re-evaluation of their phylogenetic relationships .