Studies on vegetation recovery in an island ecosystem in the Bonin Islands

我们调查了直接和间接的影响，外来灌木，银合欢，随后建立本地中期演替树，木荷mertensiana在早期演替阶段在Chichijima岛，在日本的亚热带海洋岛屿入侵。比较了优势种和牙买加海桑对两种生境下的墨田海桑种子萌发和移栽苗生长的影响。在白头叶蝉优势地建群的牙买加石楠生长量低于东方木蠹蛾优势地。在新银合欢优势地的墨尔豆种子萌发率和幼苗生长速率均低于东方红豆杉优势地。这些结果表明，在白头忍冬入侵的群落中，白头忍冬直接抑制了墨氏墨等位酶分析结果表明，B群体中存在两个遗传隔离群。而分布格局或株数不受遗传多样性水平的影响。在所有类群中，海洋特有种的遗传多样性都很高，且大多数多样性都存在于居群内。高遗传多样性和低种群分化是一种独特的特征组合，与海洋特有种的一般概念相反。

We investigated direct and indirect effects of an invasion of alien shrub, Leucaena leucocephala, on subsequent establishment of native mid-successional tree, Schima mertensiana at early-successional stages in Chichijima Island, a subtropical oceanic island in Japan. We compared effects of dominant species and S.jamaicensis on seed germination and growth of transplanted seedlings of S.mertensiana between the two sites. Growth of S.jamaicensis established at the L.leucocephala dominated site was lower than those at T.orientalis dominated site. Seed germination rate and seedling growth rate of S.mertensiana at the L.leucocephala dominated site were lower than those at the T.orientalis dominated site. These results suggest that there was a prevention of establishment of S.mertensiana caused by an inhibition of seed germination and seedling growth of S.mertensiana by L.leucocephala directly at L.leucocephala invaded communities, which potentially changed a successional pathway in the communities.The amount and distribution of genetic variations were examined in 16 populations of endemic genus Boninia and an endemic species Euodia nishimurae in Bonin Islands. Based on allozyme analysis, two genetic isolated groups were recognized in B. grisea var.grisea, while distributional patterns or numbers of trees were not affected to levels of genetic diversities. For all taxa, high genetic diversities for oceanic endemics were detected, and most of diversities were possessed within populations. High genetic diversity and low population differentiation is a unique character combination contrary to general concepts of oceanic endemics.