title: Studies of a South East Asian ant-plant association: protection of Macaranga trees by Crematogaster borneensis.
abstract: In the humid tropics of SE Asia there are some 14 myrmecophytic species of the pioneer tree genus Macaranga (Euphorbiaceae). In Peninsular Malaysia a close association exists between the trees and the small, non-stinging myrmicine Crematogaster borneensis. These ants feed mainly on food bodies provided by the plants and have their colonies inside the hollow internodes. In a ten months field study we were able to demonstrate for four Macaranga species (M. triloba, M. hypoleuca, M. hosei, M. hulletti) that host plants also benefit considerably from ant-occupation. Ants do not contribute to the nutrient demands of their host plant, they do, however, protect it against herbivores and plant competition. Cleaning behaviour of the ants results in the removal of potential hervivores already in their earliest developmental stages. Strong aggressiveness and a mass recruiting system enable the ants to defend the host plant against many herbivorous insects. This results in a significant decrease in leaf damage due to herbivores on ant-occupied compared to ant-free myrmecophytes as well as compared to non-myrmecophytic Macaranga species. Most important is the ants' defense of the host plant against plant competitors, especially vines, which are abundant in the well-lit pioneer habitats where Macaranga grows. Ants bite off any foreign plant part coming into contact with their host plant. Both ant-free myrmecophytes and non-myrmecophytic Macaranga species had a significantly higher incidence of vine growth than specimens with active ant colonies. This may be a factor of considerable importance allowing Macaranga plants to grow at sites of strongest competition.
authors.affiliation: Zoologisches Institut der Universität, Siesmayerstrasse 70, D-6000, Frankfurt/M., Federal Republic of Germany.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Fiala
authors.affiliation: Zoologisches Institut der Universität, Siesmayerstrasse 70, D-6000, Frankfurt/M., Federal Republic of Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Maschwitz
authors.affiliation: Forest Research Institute Malaysia, Kepong, Selangor, Malaysia.
authors.forename: Tho Yow
authors.initials: TY
authors.lastname: Pong
authors.affiliation: Zoologisches Institut der Universität, Siesmayerstrasse 70, D-6000, Frankfurt/M., Federal Republic of Germany.
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Helbig
keywords: Ant/plant interaction; Crematogaster borneensis; Macaranga; Myrmecophytes; Protection