RAPD Variation among Quercus Species Distributed in Temperate Deciduous Forests of the Hiruzen Mountains

Abstract

Species of the genus Quercus are widespread in the northern hemisphere. In eastern Asia, Quercus serrata Thunb., Q. mongolica Fisch. ex Ledeb. var. crispula (Blume), Q. dentata Thunb. and Q. aliena Blume, which are classified into the section Prinus, are distributed in temperate deciduous forests of north-eastern China, the Korean Peninsula, and the Japanese Islands. Several presumptive hybrids of these Quercus species have been recorded in the same locations. These species of the section Prinus and the presumptive hybrids are very important for economic utilization and investigations of ecology, forest genetics, and species evolution. In the vicinity of the Hiruzen mountains, rising over Tottori and Okayama Prefectures, Japan, Q. serrata, Q. mongolica var. crispula, and Q. dentata are distributed together in temperate deciduous forests at altitudes from 550 m to 650 m. Quercus takatorensis Makino and Q. anguste-lepidota Nakai, which are presumed to be the intermediate types of the three Quercus species, are commonly observed in the same forests. Hashizume et al. (1994) reported that the morphological measurements and structures of leaves, cupules, and acorns of the presumptive intermediate types indicated intermediate characteristics of the three Quercus species. In fact, the flowering season of the three Quercus species overlaps each year in May, suggesting the possibility of cross pollination among them in the Hiruzen Forest of Tottori University Forests (Lee, unpublished data). However, there is no direct evidence to prove natural interspecific hybridization occurring among the species of the section Prinus. In general, genetic markers have many potential applications in forest genetics and tree breeding research, including genetic diversity, population structure, phylogeny, mating systems, and tree classification. The lack of suitable markers has hindered the direct analysis of genetic structures in plant species. Isozymes have been useful to estimate genetic diversity of plant populations (Hokanson et al., 1993; Hyun et al., 1987). The isozyme analysis has an advantage in its simplicity and rapidity, however, orffy a limited number of polymorphic loci are available for use as genetic markers. Recently, a method for comparing random amplified poly1Present address: 5-72-4, Tachikawa-cho, Tottori 680,