Origin and evolution of endemic plants of the Bonin (Ogasawara) Islands
Origin and evolution of endemic plants of the Bonin (Ogasawara) Islands
复制标题
小笠原群岛特有植物的起源和进化
DOI：
10.1007/bf02763405
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
M. Ito
中科院分区：
文献类型：
--
作者：
M. Ito
小笠原群岛是典型的海洋岛屿，位于北太平洋西部，日本本土以南约1 000公里。这个群岛由大约20个小岛组成。虽然由于面积小和环境多样性有限，小笠原群岛的植物多样性很低，但与其他著名的海洋岛屿一样，小笠原群岛拥有独特的特有植物群。本文简要总结了最近对小笠原群岛特有植物群的研究结果。本文从海岛特有植物群的迁移、建立、扩大和多样化四个阶段对研究结果进行了评述。该植物群的祖先大多起源于热带和亚热带的东南亚或日本大陆，起源于罕见的远距离扩散事件。与其他海洋岛屿相比，鸟类散布物种的比例相对较高。从一些特有物种的等位酶变异获得的遗传数据集表明，迁移发生在几百万年前，遗传多样性与当前的人口规模相关。在建立时，自交亲和植物预计将具有优势。但雌雄异株植物的比例相对较高。这部分是由于在小笠原群岛的两个属中发生了从雌雄同体祖先到雌雄异株祖先的进化变化。此外，也有一些例子，从草本祖先的进化变化到木本特有种。在某些属中发现了适应性辐射，尽管同属特有种的数量不到5种。对海桐属、山矾属和Crepidiastrum的等位酶变异的研究表明，尽管它们的形态特征不同，但同属种之间的遗传一致性通常很高。这一结果表明，这些物种的分歧发生在最近，而不同的形态差异是基于数量有限的遗传变化。
The Bonin Islands are typical oceanic islands, located at the western part of the North Pacific Ocean and approximately 1,000 km south of mainland Japan. This archipelago consists of about 20 small islands. Although floristic diversity is low due to the small area and limited environmental diversity, the Bonin Islands harbor unique endemic flora as in other well-known oceanic islands. This paper presents a brief summary of the results obtained from recent studies on the endemic flora of the Bonin Islands. The results are reviewed in relation to the four stages of the evolution of endemic flora in the oceanic islands; migration, establishment, enlargement and diversification. The ancestors of the flora originated mostly from tropical and subtropical Southeast Asia or mainland Japan by rare events of long distance dispersal. The proportion of bird-dispersed species is relatively high as for other oceanic islands. Genetic data sets obtained from allozyme variation in some endemic species suggest that migration occurred several million years ago and genetic diversity is correlated with current population size. At the time of establishment, self-compatible plants are expected to have an advantage. However, the percentage of dioecious plants is relatively high. This is partly due to evolutionary changes from hermaphroditic ancestors to dioecy which occurred in two genera in the Bonin Islands. In addition, there are some examples of evolutionary changes from herbaceous ancestors to woody endemics. Adaptive radiation is found in some genera, although the number of congeneric endemic species is less than five. Studies of allozyme variation inPittosporum, Symplocos andCrepidiastrum showed that genetic identity is generally very high between congeneric species in spite of their distinct morphologies. This result suggests that divergence of these species occurred rather recently and distinct morphological differences are based on a limited number of genetic changes.