Asynchronous and synchronous updating in individual-based models

The use of mathematical and simulation models is widespread in ecology, and individual-based models (IBMs) have proved valuable for exploring individually-explicit interactions and behaviour. The success of a model will depend upon its design and the different assumptions made during construction. In particular, methods implemented in the model to deal with interactions between objects are of fundamental importance for producing appropriate results. Asynchronous and synchronous scheduling are two methods for updating object characteristics during interaction. The consequence of these updating methods has been investigated for cellular automata, but not for IBMs. Here, we assess the two methods for their potential to give different results in a deliberately simple IBM. We show that the two methods produce different results, particularly at high population densities and for increasing interaction complexity (e.g. increasing numbers of trophic levels). This work appears to be the first evidence of the importance of scheduling methods on emergent properties for individual-based models and consequently individually-explicit interactions and behaviour in ecology.