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Evolutionary Ecology Laboratory
Research projects in the Evolutionary Ecology Lab address questions of adaptation and life-history evolution in a wide variety of organisms. Three project areas are under active investigation:
These projects are described in further detail in the links above.
Collective behaviour in ant colonies
Ant societies are not directed by informed central decision makers, yet colonies diplay obvious organisation and respond 'intelligently' to changing conditions. It has become apparent that much of this organised group behaviour is achieved through self-orgnisational processes that arise from the collective outcome of simple individual actions. These individual actions are regulated by diffuse infomation spread among many workers (Deneubourg and Goss 1989; Bonabeau et al. 1997).
In the Evolutionary Ecology Lab, we are studying collective behaviours in two groups of ants: the leaf-cutting ants in the genus Atta of Central and South America, and the Argentine ant Linepithmea humile, which has been introduced into Australia (and many other parts of the world).
Atta colonies are among the largest social groups in the world, with upwards of 106 workers in a mature colony. Foragers travel along paths cleared through forest floor litter to vegetation sources, where the ants dissect leaves and carry the fragments back to their nest. The fragments serve as a substrate in the cultivation of a fungus, which in turn is harvested as a food supply for the brood. Our field work in Panama, Costa Rica and Venezuela has shown that foraging ants do not maximise their individual foraging performance (using several indices of individual performance) (Burd 1996, 2000, 2001). It might be expected that individual achievement matters less than collective gains, but it is not clear what factors govern group foraging in these ants. A Ph.D. student from our lab, Ellie Clark, has been working at the Smithsonian Tropical Research Institute in Panama to study the role of caste differentiation in the foraging behaviours of Atta colombica. We are also applying ideas from traffic engineering to study the flow of foraging ants along the cleared trails they construct. There are intriguing similarities and differences between ant traffic and human road or pedestrian traffic (Burd et al. 2002).
In Melbourne, Ph.D. student Julianne Halley is using lab colonies of Argentine ants to study group size effects on the rate and architecture of underground nest construction. Modern imaging techniques like computer-aided tomography allow three-dimensional reconstructions of otherwise hidden nest chambers and passages, without distroying or disrupting the colony inside. Previous study of group size effects on out-of-nest foraging behaviours (Halley and Elgar 2001) will be extended in 2002. Group-size effects may be related to ideas of self-organised criticality, which have received considerable attention from the physical sciences.
Background information
- Bonabeau, E., G. Theraulaz, J. Deneubourg, S. Aron, and S. Camazine. 1997. Self-organization in social insects. Trends in Ecology and Evolution 12:188-193.
- Burd, M. 1996. Foraging performance by Atta colombica, a leaf-cutting ant. American Naturalist 148:597-612.
- Burd, M. 2000. Body size effects on locomotion and load carriage in the highly polymorphic leaf-cutting ants Atta colombica and Atta cephalotes. Behavioral Ecology 11:125-131.
- Burd, M. 2001. Leaf tissue transport as a function of loading ratio in the leaf-cutting ant Atta cephalotes. Ecological Entomology 26:551-556.
- Burd, M., D. Archer, N. Aranwela, and D.J. Stradling. 2002. Traffic dynamics of the leaf-cutting ant Atta cephalotes. American Naturalist (in press).
- Deneubourg, J.L., and S. Goss. 1989. Collective patterns and decision making. Ecology, Ethology, and Evolution 1:295-311.
- Halley, J.D., and M.A. Elgar. 2001. The response of foraging Argentine ants, Linepithema humile, to disturbance. Australian Journal of Zoology 49:59-69.
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