Mutualism between Macaranga plants ＆ ants in Southeast Asia

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In the plant genus, Macaranga, which has the distribution center with diversified species in Southeast Asian tropics, many myrmecophytic species are known. They have symbiosis with their respectively specific ant-plant species and depend on them for anti-herbivore defense. Macaranga myrmecophytes provide their symbiont plant-ants with food, in turn, the ants protect the plants from herbivores and competitor plants.In this study, first, we determined the interspecific variation in intensity of ant defenses among Macaranga myrmecophyte species by ant-exclusion experiments and measurements of ant aggressiveness. Second, we determined the interspecific variation in intensity of non-ant, i.e. physical and chemical, defenses by bioassays using polyphagous lepidopterans. Comparing intensities of ant and non-ant defenses among Macaranga species, it was shown that the intensities inversely correlated, and that the balance between ant and non-ant defenses differ among Macaranga species. The meas … More urement of food body production and chemical analysis revealed that interspecific variation in ant defense intensity are affected by the production and nitrogen contents of food bodies. The balance between ant and non-ant defenses change along with aging. The bioassay using polyphagous lepidopteran suggested that the balance is biased for non-ant defenses before ant colonization but biased for ant defenses after ant colonize the plant.Partnership between Macaranga myrmecophytes and Crematogaster plant-ants are highly species-specific. Field survey and manipulative experiments showed that nest-plant selection by dispersing foundress queens of plant-ant and matching between demand and supply for resource at both sides of plant and ant take important roles in generating and maintaining the high species-specificity in the partnership. Our chemical analysis and bioassays with extract of plant surface revealed that non-volatile carbon-hydrates are used by foundress ant queens for recognition of Macaranga plant species. Experimental exchange of plant-ant species showed that 'unmatched' species combination cause either inhibition of ant colony growth due to deficiency of food or relatively weak ant aggressiveness, both of which result in corruption of mutualistic relations.Relatively long-term demographic study on Macaranga myrmecophytes have shown that interspecific variation in anti-herbivore defenses, which are reflected in the variation in the balance between ant and non-ant defenses, affect the diversity in the herbivore community on or around Macaranga myrmecophytism. Less