Molecular phylogenetic geography of pan tropic sea dispersed plants

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Among the pan tropic plants there are many sea current dispersed species. For land plants the oceans act as geographical barriers to disperse, but help dispersal of those sea current dispersed plants and progress the interchange of genes between their populations. The purposes of this work are 1) to know to what extent the genetic interchanges are occurred between the pan tropically distributed species which cover such a wide range round the world. 2) To discuss the origin of sea current dispersal plants.We searched native populations of typically pan tropic species, Ipomoea pes-caprae and Canavalia rosea in coastal regions of the Pacific, Atlantic and Indian Oceans, and made population sampling of them. As a result we could cover almost their distribution area. At their populations we collected dried leaf samples for DNA analysis, dried specimens, flower specimens fixed in FAA and seeds.In I. pes-caprae there was no variation of the sequences of the regions of CPDNA examined between all the populations. It suggests I. pes-caprae frequently immigrates between populations. On the other hand, there are many variations of the sequences of the third intron of dihydrofavonol 4-reductase (DFR-B) of I. pes-caprae. This indicates that the genetic differentiations occur among populations, especially between the Pacific, Atlantic and Indian oceans.Expansions of some sea current species, Hibiscus tiliaceus, Canavalia rosea, Mucuna gigantea by sea were discussed. Sea drifted seeds and fruits on the coastal regions of the Ryukyu archipelago were identified and their sea dispersal ability were discussed.