Role of stress in evolution: From individual adaptability to evolutionary adaptation

Lack of a developmental perspective in evolutionary studies of stress has left researchers with several unresolved questions. First, how can organisms prepare for novel and extreme environmental change? The organismal ability to mount an appropriate reaction to a stressor requires recognition and evaluation of the extreme environment. How can this ability evolve in relation to stressors that are short and rare in relation to a species generation time? Stress occurs when changes in the external or internal environment are interpreted by an organism as a threat to its homeostasis. The ability of an organism to mount an appropriate response to potentially stressful environmental changes requires correct recognition of environmental change and the activation of a stress response. The costs and benefits of stress detection and stress response implementation and the costs and benefits of maintaining stress resistance strategies vary among environments and individuals, favoring multiple solutions of dealing with stress. Numerous studies have documented an increase in phenotypic and genotypic variance under stress, and it is suggested that this variance is a source of novel adaptations under changed environments. The Chapter outlines this perspective, with specific focus on the effect of stress during development in animals and suggests that these questions are resolved by considering the organization of developmental systems that enable accommodation and channeling of stress-induced variation without compromising organismal functionality; the significance of phenotypic and genetic assimilation of neurological, physiological, morphological, and behavioral responses to stressors; as well as multiple inheritance systems that transfer the wide array or developmental resources and conditions between the generations enabling long-term persistence and evolution of stress-induced adaptations.