Evolution of host plant utilization patterns in herbivorous insects viewed from molecular phylogenies of plants and herbivores

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We investigate the history and process of diversification of both the plants and their herbivores by using molecular phylogenetic techniques. We collected various groups of herbivores and their host plants from Japan, Taiwan, Burma, Malaysia, Australia, Fiji, New Caledonia and Chile for the analyses. The insect groups which we investigated are as follows: (1) leaf-miners of Diptera (Agromyzidae, Tephritidae, Pallopteridae), Lepidoptera (Gracillariidae, Agathiphagidae, Micropterigidae) and Coleoptera, (2) Seed-parasites of Gracillariidae, (3) pollinators (Apidae and other various insects).We found some interesting plant-herbivore interactions on primitive plant clades. Larvae of Mimectatina meridiana ohirai (Cerambycidae) were found mining megasporophylls and dead frond rachises of cycads. This is the first record of the cerambycid leaf-miner. I found dipteran leaf-miners on microphylls of Huperzia serratium (Lycopodiaceae) at Ashu, Kyoto. This is the first record of dipteran hervigores in Licopodiales.When studying seed-parasitic insects, we found a novel obligate pollination mutualism between Glochidion trees and its seed-parasitic gracillariid moths. In the mutualism, Glochidion trees are actively pollinated only by small, species-specific gracillariid moths which are parasitic in the developing seeds. Both the plants and seed-parasitic pollinators have experienced reciprocal diversification by maintaining their high host-specificity and mutualistic interaction. The system id the third example of obligate pollination mutualism which involves reciprocal diversification, and is comparable with the Fig-figwasp, Yucca-yucca moth mutualisms.We also investigated community-level plant-pollinator interactions at a natural grassland ecosystem at Mt. Yufu. Grassland ecosystem is one of the most endangered terrestrial habitats in Japan. We described detailed interactions between grassland plants and their pollinators for the first time.