抄録
To understand the morphological and ecological diversity of Syzygium in the Bonin Islands, we examined 269 individuals from 37 localities in the Bonin Islands and the Nansei Islands for vegetative and floral characters. The vegetation of their respective habitats was also examined as an indicator of environmental conditions. Three groups of Syzygium in the Bonin Islands were distinguishable from the Nansei Islands group by principle component analysis (PCA). These four groups had unique morphological sets. The three groups in the Bonin Islands generally grow in different vegetation and seldom occur sympatrically, suggesting habitudinal segregation among the groups. One group of plants on the Bonin Islands is distributed on both the Chichi-jima Islands and the Haha-jima Islands and shows remarkable morphological variation of the Haha-jima Islands compared with those of the Chichi-jima Islands. In particular, many individuals in the southern area of the Haha-jima Islands have peculiar morphological features not found in the others. Furthermore, these distinctive Haha-jima individuals grow in Distlylium-Schima dry forests, which are rare for this group on the Chichi-jima Islands. The morphological differentiation of this group may represent an initial stage of the evolutionary process of adapting to environmental conditions.
