SFB-TRR 212

Armament, hunger, and mating: how competition can drive individual variation

Overwhelming empirical evidence shows widespread individual differences in behaviour. Despite abundant research, we still do not entirely understand why this variation arises or persists, or what effects it has on ecology and evolution.

Previously, we used models to explore how individualised behavioural strategies influenced responses to rapid environmental change, brought about for example by anthropogenic influence. Our results revealed that only by taking individualised strategies into account, were population responses predictable. We also modelled the evolution of risk-taking when many strategies were possible. Our model showed that such an evolutionary stable strategy set is expected to consist of two and more strategies under a wide range of realistic conditions. This successful step from modelling in binary strategy space to a pseudo-continuous distribution shows that resource inequality and risks of competition should shape intraspecific variation.

Our future efforts will further expand models assuming continuous traits to examine the importance of competition between individuals in different ecological contexts. To examine the evolution and maintenance of individualised behavioural strategies, we have selected three types of competition that occur in many species, are important in evolution, and are conceptually very different from each other:

1. aggressive but costly resource monopolization
2. exploitation competition between individuals of a predatory species that prey upon deceptive mimics
3. costly signalling in inter-sexual selection, i.e. mate choice

 We will model these scenarios with individual-based models that include aspects of game theory and genetic algorithms. This will allow discrete or continuous sets of strategies to emerge, rather than being imposed by our assumptions. To explore whether behavioural variation can evolve due to frequency dependent competition of otherwise similar individuals, we will assume that the modelled behavioural strategies are genetically determined. Additional variants of the models will assume that individuals differ in state, that traits are phenotypically plastic, and that individuals can differ in their degree of niche conformance. These general modelling approaches described above will be complemented by models that we will specifically adjust to examine topics in the empirical projects within the TRR CRC.

Taken together our planned models should allow us to determine environmental conditions that select for individualised traits under competition.