From linking patches to linking theories: Cooperation in metapopulations

Abstract

Organisms in nature cooperate with one another, facilitating each other’s survival and reproduction. Since cooperators may experience reduced fitness compared to non-cooperators, why cooperation evolves has been an enigmatic question in evolutionary biology. Ecologically, due to a phenomenon called the Allee effect, small populations of cooperators can be particularly vulnerable to extinction. How do cooperators persist despite these seemingly adverse phenomena that threaten their survival on ecological and evolutionary timescales? Spatial structure is known to be one of the factors that can allow cooperation to evolve. However, the links between the ecology of Allee effects and the evolution of cooperation in spatially structured populations remain unexplored. In this thesis, I use a stochastic metapopulation framework to mathematically model the ecology and evolution of cooperation. Using numerical analyses, I reveal that small-scale Allee effects can disappear on larger spatial scales, enabling small populations to colonise spatially structured habitats. Further, I show that a metapopulation structure favours the evolution of cooperation in a situation where cooperation cannot evolve in a well-mixed population. I connect these results to metacommunity concepts, unifying the theories of cooperation and metacommunity ecology. My results suggest a mechanism rooted in metacommunity ecology, to explain the evolution of cooperation. In addition to contributing new paradigms to ecological and evolutionary theory, these findings are also relevant to applied fields such as wildlife conservation and invasion biology.