On the emergence of primitive cooperation in an environment of fluctuating resource supply

Abstract

A necessary property of cooperative behaviour in the animal kingdom is the reciprocal (or multilateral) dependence of the animals on one another for the purpose of (joint) competition for limited resources. The emergence of such patterns of dependent behaviour, whether cooperative or not, is often concurrent with the emergence of communication structures between the animals. Animal communication is always local, thus introducing an aspect of spatial localization into an otherwise homogenous population (“deme” structure, Wright 1945). In order to investigate the relation between emergent cooperation and communication, we introduce a model of primitive organisms living and reproducing in colonies (demes) connected by migration. Different migration structures are considered. Exposed to an environment in which the food resource supply is not deterministically fixed but stochastic, we first investigate whether the resulting supply uncertainty adversely affects the total carrying capacity of the colonies. We show that this is not always the case and provide a necessary and sufficient criterion. Modelling the supply uncertainty by a simple Markov process, we next explore whether a certain type of emergent communication (e.g. communication by means of waste metabolites) helps reverse the potentially adverse effect of food supply uncertainty. We distinguish between excitatory and inhibitory signalling and show that in the context of our model it is the inhibitory interpretation which provides the selective advantage. It will be shown that the higher the fidelity of the transmitted information, the larger the fitness differential derived. The paper develops a useful combination of (elementary) perturbation and stochastic averaging techniques (the first order dynamics is used to average second order terms) which may be of interest outside the application reported here.