The ants’ garden: Qualitative models of complex interactions between populations

Understanding interactions between populations is an important topic for research, management and education in ecology. However, a number of problems hamper the use of traditional modelling approaches when addressing complex systems involving three or more populations. In this paper we describe implemented qualitative models for improving understanding about the ants’ garden, a complex system consisting of ants, their cultivated fungi, a virulent parasitic fungus that may attack the garden and bacteria that produce antibiotics against the parasitic fungus. These models are based on a qualitative theory of population dynamics and use models about symbiosis, commensalisms, amensalism and parasitism to create the structure of the ants’ garden. Simulations show the effects of changes in populations affecting the whole garden behaviour. Finally, we discuss the possibility of using a qualitative approach for building conceptual models of complex systems, grounding explanations on explicit representations of the causal influences, implementing easy to change assumptions, testing different hypotheses and complementing numerical models.