Phytogeographical relationship between Madaqascar and Southeast Asia

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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.