Modelling collective behaviour to protect social insect ecosystem services

Principal Investigators: Bernd MeyerMartin Burd and Julian Garcia

Partner Investigators: Arne Traulsen and Hans-Joachim Offenberg

The project investigates how social insects adapt to environmental stress, for example due to climate change and pollution. Fundamental to the adaptibility of social insects are the complex mechanisms that allow colonies to maintain a carefully balanced division of labour (DOL). The project builds on evolutionary game theory to develop a new approach for analysing how environmental factors impact on DOL and thus colony viability. Our work combines mathematical models and computer simulations with biological experiments in the lab and field.

Social insects are one of the most fascinating examples of organised societies in the animal kingdom. These keystones of biodiversity also represent an extremely valuable agricultural asset through the significant ecosystem services they provide.

While the spotlight is usually on honey bees and pollination, social insects in general provide a much broader range of ecological services, including soil conditioning, seed dispersal, and pest control. Changing environmental conditions now render them vulnerable. Colony collapse disorder in honeybees (CCD) provides an unfortunate but clear reminder that similar problems may threaten social insect populations on a much broader scale.

While the origins of CCD are still not fully understood, it is now becoming clear that some of its causes are not specific to honeybees and could easily impact any kind of social insect. This is because they are not of a specific physiological nature but related to stress-induced behavioural changes that lead to a collapse of colony organisation. Stress arises from a number of ecological factors, including shifting climate conditions, changed agricultural practice, and inadequate nutrition. The consequences of pesticide poisoning and diseases are well investigated, but the impact of behavioural changes in response to ecological stress is far less understood.

All social insects live in elaborately organised societies. Their intricate social structures enable them to continuously manage a complex network of simultaneous tasks; from scouting and foraging to colony defence, nest building, thermoregulation, and brood care. To ensure colony survival and reproduction it is absolutely vital that the colony workforce is adequately allocated to these different tasks. Social insect colonies are able to perform such task allocation with an amazing degree of flexibility, continuously adjusting to changes in external environmental conditions and in the internal needs of the colony. The resulting division of labor (DOL) is a cornerstone of all social insect societies and commonly credited as a key factor for their enormous ecological success.

While the regulatory mechanisms underpinning DOL provide sufficient flexibility within the normal envelope of environmental conditions, it is unclear just how far this flexibility goes, and at what point colony organisation breaks down. Recent literature documents clear links between environmental stress factors and “task allocation gone wrong” for isolated aspects, but no general picture has emerged yet.

This is at least partly due to the limited power of current models of DOL. Comparatively little attention has been given to how social interactions regulate task allocation and none of the existing frameworks provides a direct link (beyond task-related stimulus levels) to integrate environmental conditions as a fundamental element into the modelling process.

The primary aim of this project is to develop a new integrative modelling approach for DOL in social insects based on evolutionary game theory (EGT) that addresses these shortcomings. Its predictions will be tested experimentally and in the field.

This work is funded by the Australian Research Council and conducted in collaboration with the Max Planck Institute for Evolutionary Biology and the Department of Bioscience at Aarhus University.

Selected publications:

  • Rui Chen, Julian Garcia, and Bernd Meyer. Social learning in a simple task allocation game. In ALife XV Workshop on multidisciplinary applications of evolutionary game theory, Cancun, Mexico, July 2016.