Abstract
The vertebrate stress response comprises a suite of behavioural and physiological traits that must be functionally integrated to ensure organisms cope adaptively with acute stressors. The expectation that natural selection has favoured functional integration leads to a prediction of genetic integration: genetic variation in the stress response should include covariation between its component behavioural and physiological traits. Despite the implications of such genetic integration for our understanding of human and animal health, as well as evolutionary responses to natural and anthropogenic stressors, formal quantitative genetic tests of this prediction are lacking. Here we demonstrate that Trinidadian guppies (Poecilia reticulata) show genetic variation in a suite of behavioural and physiological components of the acute stress response, and that these are indeed integrated into a single major axis of genetic variation. This axis appears to reflect continuous variation in the magnitude of integrated stress responsiveness, rather than variation in ‘coping style’ (a verbal model that postulates equal levels of stress responsiveness will manifest differently across individuals). The genetic integration we find here could either facilitate or constrain evolutionary responses to selection, depending upon the extent to which the direction of selection aligns with this single major axis of genetic covariation among stress response traits. Such integration also suggests that, while stress-related disease typically arises from physiological components of the stress response, selection on the genetically correlated behavioural responses to stress could offer a viable non-invasive route to the genetic improvement of health and welfare in captive animal populations.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Revisions to introduction and discussion. Figures updated. Methods and results unchanged apart from a few cosmetic edits.
