Sammendrag
Reversible phenotypic plasticity — the ability to change ones phenotype repeatedly throughout life — is likely to evolve in environments that vary predictably within an individual’s lifetime. It might also help to avoid senescence, as the mismatch between the environment and a non-plastic individual’s traits is likely bound to increase as time passes. Intriguingly, this means it is not straightforward how causalities should be understood if reversible plasticity is found to covary with lifespan. Previous models assume a unidirectional arrow of causality: investment in plasticity evolves as a response to rate of environmental variation with respect to the individual’s life history. In our study, we consider that lifespan can also evolve in response to plasticity, and model the coevolution of these two traits. Our model provides a proof-of-principle that a long life is not just a context that simply sets the stage for lifelong plasticity; plasticity itself can open doors to a longer life by helping individuals avoid becoming ‘outdated’. We find that there are conditions that predict short or long lives as well as high or low investment in plasticity. With highly autocorrelated environmental fluctuations we predict low investment in reversible plasticity and therefore a phenotype that is poorly matched to the environment at older ages. Such environments therefore select for high reproductive investment, and lifespans evolve to be relatively short. Inaccurate sampling of the environment, which we model as sampling error, can make reversible plasticity pay off less well. This is another factor that can reduce the investment in plasticity, and the knock-on effects on life histories evolve accordingly. We therefore urge empiricists and theoreticians alike to consider the possibility for life histories to evolve as a response to reversible plasticity, and not just the other way around.
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