The primary purpose of this chapter is to evaluate the consequences of deb models for individuals at the population and higher levels if extremely simple rules are defined for the interaction between individuals and the energy balance of the whole system. The first section deals with trophic interactions between species, and the constraints on parameter values that ensure a stable coexistence. Then follows a discussion of population dynamics, food chains and (simple) ecosystems.

Trophic interactions

deb theory can be used to analyse the dynamics of systems with complex types of mass exchange between the participants in trophic relationships, a rich spectrum ranging from competition to predation. The present aim is to discuss some constraints in these patterns that ensure weak homeostasis of structural masses: the relative abundance of the structural masses of the participating species is independent of the substrate densities in the environment at steady state. This matter is taken up again in the discussion on merging {406}.

Trophic relationships are hard to classify; all relationships seem to be unique at close inspection. They are usually based on the judgement of being beneficial for one or both partners, and many different definitions exist for particular inter-species relationships. The oxpecker Buphagus feeds on insects that are attracted to wounds of giraffes, antelopes and other bovids; it is not difficult to see why the thin-skinned small antelopes make evident that they do not really appreciate this ‘help’ from the birds: oxpeckers try to keep wounds attractive for insects.