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Headlines Published on 13 February 2012

NATURAL HISTORY
Title Study finds why parasites can be good for society

Ants are tough, loyal and hard workers, all working towards a common goal. New research from Germany, France and the United Kingdom suggests that political and economic theorists could learn lessons by examining how ant colonies allocate food resources. Current political systems use legislation and regulations to ensure that resources are not overexploited. The findings, presented in the journal The American Naturalist, show how ant colonies reap rewards when an external 'parasite' enters the picture, effectively helping curb resource overexploitation by resident queens. More female offspring with queen potential is the result, which in turn gives colony efficiency and fitness (or health) a big boost.

Ants = teamwork © Shutterstock
Ants = teamwork
©  Shutterstock

This study builds on extensive research conducted by researchers from the University of Würzburg in Germany, as well as from the Centre for Ecology & Hydrology of the University of Oxford, Rothamsted Research, and the University of Southampton in the United Kingdom, and the Musée National d'Histoire Naturelle, and Centre National de la Recherche Scientifique in France. They evaluated the ant colonies of Formica lemani over a six-year period and determined that these colonies, infested with larva of the predatory parasitic hoverfly Microdon mutabilis, produced a greater number of new queens than did uninfected colonies.

In this latest study, the team targeted the development of a theoretical model to simulate the possible mechanisms behind a greater number of potential new queens. The successful development of potential new queens depends on a specific level of resources. Food resources are limited when increasing worker larvae exist. The findings of the first study indicated that the presence of the parasitic hoverfly cuts the number of ant larvae, which in turn boosts the share of food available for each surviving larva including the potential new queens.

Based on the predictions of this latest model, the researchers found that predation on the young ant brood by the hoverfly could contribute to boosting the production of new queens, achieved through a re-routing of food resources.

'The allocation of food resources within an ant colony has interesting parallels in the way we manage our society and environment in a sustainable manner,' explains Dr Karsten Schönrogge, an ecologist at the Centre for Ecology & Hydrology and one of the authors of the study. 'It is easy to visualise the "Tragedy of the Commons" scenario unfolding within uninfected ant colonies, where a shared and limited resource is depleted through unregulated access, resulting in over-exploitation to the detriment of society.'

The researchers point out that while in an infected colony the presence of the hoverfly 'parasite' adversely impacts the overall larva numbers, they have a positive impact on the colony as a whole. The net effect is an increased number of new potential queens.

This latest model also predicts that the rise is triggered at the start of a Microdon infection period. The researchers note how a reanalysis of the original results showed that this prediction is supported by real world observations.

Says Dr Schönrogge: 'Ant foraging behaviour has previously been modelled by computer scientists and ecologists, resulting in the ant colony optimisation algorithm (ACO), a major advance in the computing sector. Ants are one of the most successful animal groups on the planet and the next question for ecologists and political theorists is how resource management within ant colonies might affect interactions with surrounding related or unrelated competing colonies, and how that would be mirrored in human societies.'









More information:

  • Centre for Ecology & Hydrology
  • The American Naturalist