Effects of genetic varitation in host plants on herbivourous insect communities

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In order to examine effects of genetic variation in host plants on herbivourous insect communities, we focused on relations between Japanese oaks and lepidopteran leafminers. We obtained the following results.1. Phylogenetic analysis baaed on nucleotide sequences of three genes distinguished three lineages in Japanese taxa of Quercus, Cerris-Ilex, white-oak (sensru strict) and Cyalobalanopsis.2. One new Phyllonorycter species feeding on only Q, dentata was described. The four species of nipponicella complex including this new species have specific preferences for host oaks with close relatons.3. Discriminant analysis based on several leaf traits detected 11 morphologically intermediate trees of Q. dentata and Q, crispula among 116 individuals examined in oak forest of Ishikari, Hokkaido. Of the intermediate trees, six were mined by both Q. dentata-specific and Q. crispula-specific Phyllonorycter species.4. Mine density of Phyllonorycter per leaf area often negatively correlated with le … More af size, leaf wet weight per area or leaf toughness, but densities of Caloptilia and Stigmella frequently positively correlated with them. The survival of Phyllonorycter larvae was not related to any leaf traits.5. In Q. crispula, nitrogen concentration per unit area was higher in artificially damaged leaves than in control leaves. In Q. dentata, however, it did not differ between them. Both oaks showed no difference in the density of Phyllonorycter mines between artificially damaged and control leaves.6. The similarity of parasitoid assemblages on six deciduous oaks in terms of species composition was not well accounted for by one factor such as host leafminer, host food-oak or geographic location..7 Silkmoth larvae fed by sunny leaves of Q. acutissima showed a significantly higher growth performance than those fed by shade leaves.These results suggest that not only inter- and intra-species variation but also intra-tree variation of leaf traits are important in organizing herbivorous insect communities. Less