Variable environments select for short lifespan

The role of environmental variation in the evolution of lifespan is contested. Classic theory suggests that variable environments result in evolution of long life but novel theoretical breakthroughs show that environmental variation can instead select for short lifespan when the changes are rapid relative to generation time. Here we combined simulation modelling and experimental evolution to study the evolution of lifespan in response to temperature variation to provide the first empirical test of the new theory. Genetically diverse populations of the outcrossing nematode , were exposed to a novel, stressful temperature for 30 generations, in either stable, slowly increasing or fluctuating temperature regimes. We found evolution of shorter lifespan in populations evolving in rapidly fluctuating environments both in simulation models and in real populations supporting the new theory. While climate warming is predicted to increase environmental stochasticity, our results show that fast temperature cycles rapidly select for short lifespan.