Consequences of catastrophic disturbances on population persistence and adaptations

25 The intensification and increased frequency of weather extremes is emerging as one 26 of the most important aspects of climate change. We use Monte Carlo simulation to 27 understand and predict the consequences of variations in trends (i.e., directional 28 change) and stochasticity (i.e., increase in variance) of climate variables and 29 consequent selection pressure by using simple models of population dynamics. 30 Higher variance of climate variables increases the probability of weather extremes 31 and consequent catastrophic disturbances. Parameters of the model are selection 32 pressure, mutation, directional and stochastic variation of the environment. We 33 follow the population dynamics and the distribution of a trait that describes the 34 adaptation of the individual to the optimum phenotype defined by the 35 environmental conditions 36 The survival chances of a population depend quite strongly on the selection 37 pressure and decrease with increasing variance of the climate variable. In general, 38 the system is able to track the directional component of the optimum phenotype. 39 Intermediate levels of mutation generally increase the probability of tracking the 40 changing optimum and thus decrease the risk of extinction of a population. With 41 high mutation, the higher probability of maladaptation decreases the survival 42 chances of the populations, even with high variability of the optimum phenotype.