An individual-based model of a tritrophic ecology

A spatially explicit individual-based model for a predator, prey and plant ecosystem is considered. The movement of the individuals is solely based on nearest-neighbour attraction/repulsion and reproduction is asexual. In this simple model emergent spatial organization of the individuals into clusters or groups is present even though all the individuals (predators and prey) are intra-specifically repelled by each other. The model ecosystem was used to determine whether an intra-specific attraction among the prey could increase their individual fitness. The attraction mechanism considered is such that when a prey is not affected by a predator or a plant then this prey is attracted to its nearest-neighbour prey. Under the assumptions of the parameterized model ecosystem, this mechanism seems highly selective on the individual level and it is evident that a population-based model could not assess this attraction mechanism. The main objective of this paper is to formalize mathematically an individual-based model and provide an example of a model tritrophic ecosystem that has the capabilities to assess evolutionary aspects of social behaviour in a prey species. (c) 2008 Elsevier B.V. All rights reserved.