Biomechanics and ecology of Macaranga–ant mutualisms
Almost all land ecosystems have been shaped by interactions between plants and insects. Biomechanical factors play a key role in these interactions, and have led to manifold adaptations of both partners. This project aims to investigate the mutualism between ants and Macaranga trees as a model for the complex ecological and evolutionary effects of biomechanical factors. Many Macaranga ant-plants possess slippery waxy stems which limit access for insects, but their ant partners are "waxrunners" capable of climbing the stems without difficulty. Macaranga "wax barriers" not only protect the ant partners against predators and competitors but also act as an ecological isolation mechanism separating different species of ant associates. The mechanisms of wax-running and the relevant adaptations are still unclear, and will be studied using 3D high-speed motion analysis, force measurements and microscopy. The effects of the plant’s wax layer morphology and the ants’ tarsal structures on attachment forces and climbing success will be studied. Species of waxrunners and non-waxrunners will be compared to identify key adaptations. Field work in SE Asia will focus on the ecological implications of wax barriers and wax-running ability and the mechanisms underlying host-specificity. Colony transplantation experiments will test to what extent the ants’ host plant choice and wax-running ability are inherited or learned. Plant and ant adaptations will be mapped onto existing phylogenies, and comparative analyses will trace their evolutionary history. The Macaranga-ant mutualism represent a unique model system for developing and testing insect-repellent surfaces for pest control.
- Federle W, Maschwitz U, Fiala B, Riederer M & Hölldobler B (1997). Slippery ant-plants and skilful climbers: Selection and protection of specific ant partners by epicuticular wax blooms in Macaranga (Euphorbiaceae). Oecologia 112: 217-224.
- Federle W & Rheindt F (2005). Macaranga ant-plants hide food from intruders: correlation of food presentation and presence of wax barriers analysed using phylogenetically independent contrasts. Biol. J. Linn. Soc. 84: 177-193.
- Feldhaar H, Gadau J & Fiala B (2010). Speciation in obligately plant-associated Crematogaster ants: host distribution rather than adaption towards specific hosts drives the process. In: Glaubrecht M, ed. Evolution in Action: Springer Berlin Heidelberg. 193-213.