Evol Ecol Res 17: 395-405 (2016)     Full PDF if your library subscribes.

Evolution of stress reactivity in stickleback

Carole Di Poi1, Jennyfer Lacasse1, Sean M. Rogers2 and Nadia Aubin-Horth1

1Département de Biologie & Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec City, Québec, Canada and  2Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada

Correspondence: N. Aubin-Horth, 1030 avenue de la Médecine, Québec, QC G1V 0A6, Canada.
e-mail: nadia.aubin-horth@bio.ulaval.ca


Hypothesis: The stress response involves a series of endocrine cascades that allow an individual to cope with real or perceived stressors to maintain a normal state. Although differences in stress response have been reported between populations facing distinct ecological challenges, whether these responses originate from genetic variation or environmental effects remains unclear. If the variation is genetically based, it could be the result of natural selection.

Question: Does variation in stress response reflect genetic variation?

Organism: Threespine stickleback (Gasterosteus aculeatus) originating from two contrasting habitats (a freshwater and a marine population).

Methods: We reared threespine stickleback originating from freshwater and marine populations in a common environment. We exposed them to a 30-minute confinement stress. We measured their ventilation rates during the first and thirtieth minutes of exposure. We also quantified whole-body cortisol concentration in fish from both populations assigned either to an undisturbed control group or to the 30-minute confinement stress.

Results: Marine stickleback exhibited significantly higher stress reactivity as inferred from the ventilation rates. Marine fish also showed higher inter-individual variation in reactivity than freshwater individuals. For all fish there was a strong response in cortisol concentration to the confinement stress. However, the extent of the response differed between the two populations, with freshwater fish showing a more marked change in cortisol concentration.

Conclusion: Genetic variation underlying divergence in stress reactivity is correlated with differences between marine and freshwater habitats.

Keywords: evolution, Gasterosteus aculeatus, natural selection, standing genetic variation, stress reactivity, threespine stickleback, ventilation rate.

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