Different combinations of multiple defence traits in an extrafloral nectary‐bearing plant growing under various habitat conditions

Summary The effects of multiple defence traits on herbivory under different abiotic conditions have not been reported in the literature. To clarify the relations between plant defence traits and abiotic factors in the field, we investigated the plasticity of multiple defence traits in young Mallotus japonicus growing in three habitat conditions: open sites, forest edges and treefall gaps. The plants used multiple defence traits differently in three habitats. At open sites, trichomes, pellucid dots and extrafloral nectaries (EFNs) were expressed better than at the treefall gaps, but food bodies (lipid-rich particles) were fewer. Fewer ants were observed on the plants at open sites than on plants in other habitats. Leaves collected from the open sites were consumed less by the generalist herbivore, Spodoptera litura, than leaves collected from the other habitats. The effect of ants on herbivore exclusion was not readily apparent at open sites. Light intensity at the open sites was high. Soil water contents were low. Tolerance was greater in the forest edge condition, where light intensity and soil water contents were intermediate. Synthesis. The defence tactics of EFN-bearing plants in the field must be determined considering the complex effects of different abiotic factors. Each plant can change its combination of defence traits in response to abiotic habitat conditions.