Genetic integration of behavioural and endocrine components of the stress response

Abstract

22The stress response is a product of selection for an integrated suite of behavioural and 23 physiological traits that facilitate coping with acute stressors. As such, genetic variation 24 in the stress response is expected to reflect genetic variation in, and genetic covariation 25 among, its behavioural and physiological components. Such genetic integration among 26 stress response components has yet to be formally demonstrated using multivariate 27 quantitative genetics, despite its profound implications for optimising human and 28 animal health and understanding the responses of wild populations to natural and 29 anthropogenic stressors. Here we use a laboratory population of wild-derived 30 Trinidadian guppies (Poecilia reticulata) to determine levels of genetic variation in 31 behavioural and physiological components of the acute stress response, and to establish 32 whether such variation is integrated into a single major axis of genetic (co)variation. 33 First, using a novel method to characterise behavioural components of the stress 34 response from a widely used Open Field Trial paradigm, we find genetic variation in, 35 and genetic covariation among, behavioural parameters that characterise movement 36 patterns under stress. Second, we find a strong genetic component to variation in both 37 the endocrine response to a confinement stressor and the rate at which this response 38 attenuates following repeated exposures to the stressor. Finally, we show that these 39 behavioural and physiological components of the stress response align on a major axis 40 of genetic (co)variation as predicted, suggesting correlational selection in the past has 41 led to genetic integration. This genetic integration could either facilitate or constrain 42 future responses to selection, depending upon the extent to which the direction of 43 selection aligns with this major axis of genetic covariation among stress response traits.44 This genetic integration also suggests that, while stress-related disease typically arises 45 from physiological stress responses, selection on the genetically correlated behavioural 46 responses could offer a viable non-invasive route to the genetic improvement of health 47 and welfare in captive animal populations.

Non-genetic maternal effects shape individual differences in cortisol phenotypes in wild chimpanzees

“…60%; Gustafsson et al, 2011), and more controlled laboratory (e.g. 28%; Houslay et al, 2019) or wild experimental animal studies (e.g. 40%; Bairos-Novak et al, 2018) in which GC variation was directly manipulated by the observers.…”

The relative speed of the glucorticoid stress response varies independently of scope and is predicted by environmental variability and longevity across birds

“…In all of our analyses, we modeled corticosterone changes after disturbance as within-individual reaction norms, drawing on the growing literature and methods that have been developed for this type of data from behavioral studies (e.g., Allegue et al, 2017; Hertel et al, 2020). A number of conceptual reviews have suggested that physiological stress responses should be considered as reaction norms (Hau et al, 2016; e.g., Taff and Vitousek, 2016; Wada and Sewall, 2014), but relatively few empirical studies have explicitly taken this approach to date (but see, Fürtbauer et al, 2015; Houslay et al, 2022) and we are not aware of any comparative papers that have modeled corticosterone responses as reaction norms.…”

Endocrine flexibility can facilitate or constrain the ability to cope with global change.

“…There is ample evidence both that thermal flexibility occurs in hormones and that hormones in turn support physiological, behavioral, and morphological traits that likely promote thermoregulation, evading unfavorable conditions, or temperature related changes in behaviors that influence fitness. For example, glucocorticoids mediate changes in behavior, such as foraging, locomotion, and parental care in individuals [38]; although studies showing covariation of flexibility for glucocorticoids and flexibility in behavior at the individual level are rare [but see 74]. Behavioral thermoregulation involves moving to the shade, forgoing foraging [73], reducing chick provisioning in high heat [75,76] or moving to different places [77], among others.…”