Geometry explains the benefits of division of labour in a leafcutter ant

Helanterä, Heikki and Ratnieks, Francis L W (2008) Geometry explains the benefits of division of labour in a leafcutter ant. Proceedings of the Royal Society, 275 (1640). pp. 1255-1260. ISSN 1471-2954

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Abstract

Many ant species have morphologically distinct worker sub-castes. This presumably increases colony efficiency and is thought to be optimized by natural selection. Optimality arguments are, however, often lacking in detail. In ants, the benefits of having workers in a range of sizes have rarely been explained mechanistically. In Atta leafcutter ants, large workers specialize in defence and also cut fruit. Fruit is soft and can be cut by smaller workers. Why, therefore, are large workers involved? According to the geometry hypothesis, cutting large pieces from three-dimensional objects like fruit is enhanced by longer mandibles. By contrast, long mandibles are not needed to cut leaves that are effectively two-dimensional. Our results from Atta laevigata support three predictions from the geometry hypothesis. First, larger workers cut larger fruit pieces. Second, the effect of large size is greater in cutting fruit than leaves. Third, the size of fruit pieces cut increases approximately in proportion to the cube of mandible length. Our results are a novel mechanistic example of how size variation among worker ants enhances division of labour.

Item Type: Article
Additional Information: Issue: 1640
Schools and Departments: School of Life Sciences > Evolution, Behaviour and Environment
Subjects: Q Science
Depositing User: Francis Ratnieks
Date Deposited: 06 Feb 2012 20:43
Last Modified: 26 Jun 2013 10:15
URI: http://srodev.sussex.ac.uk/id/eprint/27661
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