Developmental plasticity of immune defence in two life-history ecotypes of the garter snake, Thamnophis elegans - a common-environment experiment

Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA 50010, USA.
Journal of Animal Ecology (Impact Factor: 4.5). 03/2011; 80(2):431-7. DOI: 10.1111/j.1365-2656.2010.01785.x
Source: PubMed


1. Ecoimmunological theory predicts a link between life-history and immune-defence strategies such that fast-living organisms should rely more on constitutive innate defences compared to slow-living organisms. An untested assumption of this hypothesis is that the variation in immune defence associated with variation in life history has a genetic basis.
2. Replicate populations of two life-history ecotypes of the garter snake Thamnophis elegans provide an ideal system in which to test this assumption. Free-ranging snakes of the fast-living ecotype, which reside in lakeshore habitats, show higher levels of three measures of constitutive innate immunity than those of the slow-living ecotype, which inhabit meadows around the lake. Although this pattern is consistent with the ecoimmunological pace-of-life hypothesis, environmental differences between the lakeshore and meadow habitats could also explain the observed differences in immune defence.
3. We performed a common-environment experiment to distinguish between these alternatives. Snakes born and raised in common-environment conditions reflected the immune phenotype of their native habitats when sampled at 4 months of age (i.e. fast-living lakeshore snakes showed higher levels of natural antibodies, complement activity and bactericidal competence than slow-living meadow snakes), but no longer showed differences when 19 months old.
4. This suggests that the differences in innate immunity observed between the two ecotypes have an important – and likely age-specific – environmental influence, with these immune components showing developmental plasticity. A genetic effect in early life may also be present, but further research is needed to confirm this possibility and therefore provide a more definitive test of the ecoimmunological pace-of-life hypothesis in this system.

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Available from: Maria G. Palacios
    • "This divergence in life-history strategies, despite significant gene flow between populations (Arnold 2005, 2006), is putatively driven by differing thermal regimes (Bronikowski 2000), resource availability (Bronikowski and Arnold 1999;Miller et al. 2011), and predation rates (Sparkman et al. 2013). Studies in this system have demonstrated ecotypic differences in immune investment (Sparkman and Palacios 2009;Palacios et al. 2011), endocrine function (Palacios et al. 2012), cellular repair efficiency (Robert and Bronikowski 2010), and stress response pathways (Schwartz and Bronikowski 2012). Adult L-fast snakes have higher resting metabolic rates than M-slow snakes across 157–327C (Bronikowski and Vleck 2010), but this ecotypic difference was not present in month-old snakes reared under common laboratory conditions (Robert and Bronikowski 2010), which suggests that developmental habitats have permanent effects of metabolic rate. "
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