Dr Tim Rogers, University of Bath: Strength in numbers: how demographic noise can reverse the direction of selection

Deterministic evolutionary theory robustly predicts that populations displaying altruistic behaviours will be driven to extinction by mutant cheats that absorb common benefits but do not themselves contribute. In this talk I will show how demographic stochasticity can in fact reverse the direction of selection in favour of the cooperative phenotype if their behaviour appreciably alters the carrying capacity of the population. I will present an analysis of a simple but general mathematical model of evolutionary population dynamics in the specific context of public goods production, and derive conditions for stochastic selection reversal.