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Title: Spatial and temporal organisation within ant societies
Author: Richardson, Thomas Owen
ISNI:       0000 0004 2720 5786
Awarding Body: University of the West of England, Bristol
Current Institution: University of the West of England, Bristol
Date of Award: 2010
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In this thesis the organisation of colonies of the ant, Temnothorax albipennis, is investigated with a special focus on their spatial and temporal statistics. Individual-based modelling combined with analyses of experimental data are used extensively to infer the mechanisms that govern individual and collective behaviour. The unequal allocation of labour amongst different individuals, as manifested in skewed distributions of activity, is ubiquitous within the social insects. Early non-spatial individual-based models demonstrated that such skewed divisions of labour can self- organise through the interaction of fluctuating levels of stimuli associated with a task, with differentially sensitive agents that perform work upon the stimulus. Here, that modelling framework is extended by explicitly including space. This modification induces a 'percolation' effect, in which small differences amongst agents in their response thresholds, are related to large differences in their probabilities of performing work. The extension of the original fixed-threshold models of Division of Labour to include space means that they can be treated as a special case of diffusion in disordered media - a well studied branch of statistical mechanics. Staying at home to care for young or leaving to find food is one of the most fundamental divisions of labour. Here the rate of departures from ant nests and the collective activity of the individuals within the nest, are experimentally quantified. Both the rate of nest-leaving, and the inside-nest activity showed a non-linear decline over time. This and other results indicates that fluctuating record signals and repulsive ant-ant interactions play a significant role in colony organisation. A record signal is a new 'high water mark' in the history of a system. The dynamics of several complex but purely physical systems are also based on record signals but this is the first time they have been experimentally shown in a biological system. Finally, the generation of spatial pattern formation is experimentally investigated In the context of resilience to perturbations. The brood within the ant colony is often sorted into an intricate annular pattern, according to the developmental stage of the various rood types. Even after the pattern is completely destroyed, the workers are able to re-establish the pattern. The dynamics of this process of re-emergence is quantified in detail. Lastly, the possible utility of the pattern as a spatial cue to the workers is discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available