Difference in intensity of ant defense among three species of Macaranga myrmecophytes in a southeast Asian dipterocarp forest

To examine interspecific variation in the intensity of ant defense among th ree sympatric species of obligate myrmecophytes of Macaranga (Euphorbiaceae ), we measured the ratio of ant biomass to plant biomass, ant aggressivenes s to artificial damage on host plants, and increase in herbivore damage on host plants when symbiont ants were removed. increase in herbivore damage f rom two- and four-week ant exclusion varied significantly among the three s pecies. The decreasing order of vulnerability to herbivory was M. winkleri, M. trachyphylla, and M. beccariana. The ant/plant biomass ratio (= rate of the dry weight of whole ant colonies to the dry weight of whole abovegroun d plant parts) and ant agressiveness also varied significantly among the th ree species; the orders of both the ant/plant biomass ratio and ant aggress iveness were the same as in the herbivory increase. These results indicated that the intensity of ant defense differs predictably among sympatric spec ies of obligate myrmecophytes on Macaranga. In addition to the interspecifi c difference in the total intensity of ant defense, when symbiont ants were excluded, both patterns of within-plant variation in the amount of herbivo re damage and compositions of herbivore species that caused the damage diff ered among species. This suggests that the three Macaranga species have dif ferent systems of ant defense with reference to what parts of plant tissue are protected and what herbivorous species are avoided by ant defense. Thus , it is important to consider the interspecific variation in ant defense am ong Macaranga species to understand the herbivore community on Macaranga pl ants and the mechanisms that promote the coexistence of multiple Macaranga myrmecophytes.