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Stochastic Population Biology in a Fluctuating Environment

Final Report Summary - STOCHPOP (Stochastic Population Biology in a Fluctuating Environment)

STOCHPOP has contributed to a new synthesis integrating ecological and evolutionary processes. This synthetic approach was based on the fundamental premise that the effects of environmental stochasticity are essential for the understanding of biological processes at every time scale because all natural populations are exposed to a fluctuating environment. In this project we have produced a statistical toolkit that allows us to estimate how stochastic effects as well as density-dependent feed-back mechanisms affect ecological and evolutionary dynamics. We have used these methods to achieve three major conclusions mainly based on long-term data sets of populations of birds, mammals and marine fishes: First, the ecological effects of a fluctuating environment can be predicted from some basic set of life history characteristics distributing species along a slow-fast continuum of life history variation. Secondly, effective population sizes determining the loss of genetic diversity is in general density-dependent. Thirdly, density-dependence in the population dynamics affects the strength of fluctuating selection caused by environmental change, which can result to r- and K-selection. This means that phenotypes favoured at small population sizes can be selected against at high-densities, resulting in balancing selection around an intermediate phenotype. This is an important general mechanism, strongly affecting how rapid adaptations to an altered environment can evolve. Thus, our project has demonstrated that processes previously ignored in evolutionary studies may strongly affect Darwinian evolution.