Volume 15, Number 36: 5 September 2012
"In the face of rapid environmental change," in the words of Meylan et al. (2012), "populations may persist, given sufficient time, by dispersal and shifting distributions that track their original environment (Holt, 1990; Parmesan, 2006)." In addition, they say that "a second compensatory response is adaptation by microevolution to new ecological conditions," or what they describe as thermal adaptation (Chown et al., 2010; Sinervo et al., 2010; Huey et al., 2012)." Yet a third means by which they say that "individuals within a population may persist in rapidly changing environments" is by "behavioral or physiological compensation, i.e. phenotypic plasticity (Parmesan, 2006; Charmantier et al., 2008; Canale and Henry, 2010; Fuller et al., 2010)," which phenomenon may entail "within-individual plasticity (i.e. acclimatization within or across years), genotype x environment interactions (i.e. the reaction norm of a trait to the current environment) or developmental plasticity (Visser, 2008)." And in their review of the subject of phenotypic plasticity, Meylan et al. (2012) focus on "the role of hormonally mediated maternal effects in inducing phenotypic plasticity as a response to rising temperatures and extreme climatic events," citing the earlier work of Marquis et al. (2008).
So what does the review of the three researchers reveal? First of all, it describes how the discovery of maternal androgens and glucocorticoids in egg yolks, together with the intra-clutch variation of these hormones (Groothuis and Schwabl, 2008), make it possible for the offspring phenotype to be "manipulated in response to environmental conditions experienced by the female (Weaver et al., 2004)," so that this maternal effect can be considered to be a form of "intergenerational phenotypic (developmental) plasticity," which could well prove crucial "in coping with unpredictable environments." And in this regard, they indicate that "hormones are a critical link between the environment and the genome," in that they "may mediate the expression of phenotypic variation, generate trait integration, shape multivariate trade-offs (Sinervo et al., 2008) and either directly or indirectly shape phenotypic plasticity during ontogeny and later into adulthood (Lessells, 2008)."
In further discussion of the topic, Meylan et al. state that "the hormonal cascades involved in organizational effects during development may be modulated by environmental stressors and the maternal response as given by the duration and magnitude of elevated glucocorticoids." And they go on from there to thoroughly discuss "the phenotypic and population dynamic consequences of prenatal exposure to steroid hormones resulting in context-dependent expression of traits by the offspring," ultimately describing "how hormone-mediated maternal effects may enhance rapid adaptation to changing environmental conditions."
Last of all, the three ecologists write that "females exposed to abiotic stressors during reproduction may alter the phenotypes by manipulation of hormones to the embryos," and they conclude, therefore, that "hormone-mediated maternal effects, which generate phenotypic plasticity, may be one avenue for coping with global change." And a good one it is!
Sherwood, Keith and Craig Idso
References
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