Behavioral Variability and Limits to Evolutionary Adaptation under Stress

Abstract

Publisher Summary Energy expenditure is a prerequisite for organisms to exist in any habitat, as exposure to biotic and especially abiotic stress is the norm in free-living populations. Therefore, the distribution and abundance of organisms can be related to energy balances, derived from the costs of various stresses interacting with gains from resources. Consequently, the behavioral selection of preferred habitats imposing low energy costs is adaptive. On the other hand, adaptation is limited when available energy becomes totally restrictive. Therefore, energetically costly behaviors, especially those involving sexual selection, are important in determining limits. Heterozygotes tend to be favored in extreme environments because of their energy and metabolic efficiency. Therefore, genetic variability is unlikely to be restrictive in stressed free-living outlier populations; however, ecological circumstances can preclude the survival of novel variants. Under stressed free-living conditions, favored good genotypes are likely to be stress resistant and heterozygous. An association among success in mating, the development of extreme sexual ornaments, rapid development, and a long life can be postulated based on the metabolic efficiency of stress-resistance genotypes. While these postulated associations among fitness traits are supported by only limited empirical evidence, they may be important in any habitat where organisms are close to their limits of survival.