Investing for survival of rare severe stresses in heterogeneous environments

We model the ESS investment of limiting resources for survival of rare severe stresses, with an emphasis on investment by trees in mechanical strength for survival of storm stresses. The basic model includes the effects of the fitness benefits of increased survival, the cost in reproduction, the effects of the distributions and timing of the stress in the population, and of stress-independent mortality. The ESS investment in survival of unsynchronized stresses increases if stress-independent mortality decreases, and if the cost of the resistance decreases. The ESS investment increases, and then decreases, when the probability of extreme stresses increases. The fitness of each individual increases if the allocation of resources for resisting stress is optimally adapted to its local stress probability distribution. A Bayesian model is constructed for updating the estimate of the local stress probability distribution, which each individual can get from the exposure to sub-lethal stresses during its life. This estimate can then be used for the ESS investment. The results are discussed and applied to a wider class of organisms, stresses and resistance mechanisms.