Adaptation and extinction in changing environments.

The extinction risk of a population is determined by its demographic properties, the environmental conditions to which it is exposed, and its genetic potential to cope with and adapt to its environment. All these factors may have stochastic as well as directional components. The present chapter reviews several types of models concerned with the vulnerability of small populations to demographic stochasticity and to random and directional changes of the environment. In particular, the influence of mutation and genetic variability on the persistence time of a population is explored, critical rates for environmental change are estimated beyond which extinction on time scales of tens to a few thousand generations is virtually certain, and the extinction risks caused by the above mentioned factors are compared.