Phytogeographical relationship between Madaqascar and Southeast Asia

我们得到了一些分子数据，表明生长在马达加斯加热带雨林中的几种蕨类植物是通过远距离扩散起源于东南亚的。可能存在风孢子传播的基因循环流动。在这个研究项目中，为了验证这一假设，我们试图比较马达加斯加和东南亚(马来西亚和印度尼西亚)几种蕨类植物以及一些种子很小的被子植物的遗传同一性。我们从这两个相距较远的地区采集了相同或相近的植物，如紫背天牛复合体、单边膜质膜复合体、猪笼草、塔卡和蒲公英，测定了它们的rbcL等叶绿体基因的核苷酸序列，并分析了核基因编码的等位酶变异。我们还用扫描电子显微镜观察比较了花粉或孢子的形态。这些数据有力地表明，马达加斯加和相距6000公里的东南亚之间存在着频繁的基因交流，这些植物物种的小孢子或种子适合于通过风进行远距离传播。由此可见，这两个地区之间存在着密切的联系。

We got several molecular data suggesting that several fern species growing in tropical rain forests of Madagascar originated from Southeast Asia by long distance dispersal. There might exist recurrent gene flow by wind spore dispersal. In this research project, in order to test the hypothesis, we' tried to compare genetic identities of several fern species as well as some angiosperm species with very small seeds between Madagascar and Southeast Asia (Malaysia and Indonesia). We collected the same or closely related plant species such as Asplenium nidus complex, Hymenasplenium unilaterale complex., Nepenthes, Tacca and Dandelion species both from the two distant regions and determined their nucleotide sequences of chloroplast genes such as rbcL, and analyzed allozyme variations coded by nuclear genes. We also observed and compared pollen or spore morphology using SEM. The obtained data strongly suggested that plant species with small spores or seed which are suitable for long distance dispersal by wind, had gene exchange frequently between Madagascar and Southeast Asia which are 6,000 km apart to each other. Thus, close relationship between the two regions was indicated by this research project.