Opinion
Testing the beneficial acclimation hypothesis

https://doi.org/10.1016/S0169-5347(01)02384-9Get rights and content

Abstract

Recent developments in evolutionary physiology have seen many of the long-held assumptions within comparative physiology receive rigorous experimental analysis. Studies of the adaptive significance of physiological acclimation exemplify this new evolutionary approach. The beneficial acclimation hypothesis (BAH) was proposed to describe the assumption that all acclimation changes enhance the physiological performance or fitness of an individual organism. To the surprise of most physiologists, all empirical examinations of the BAH have rejected its generality. However, we suggest that these examinations are neither direct nor complete tests of the functional benefit of acclimation. We consider them to be elegant analyses of the adaptive significance of developmental plasticity, a type of phenotypic plasticity that is very different from the traditional concept of acclimation that is used by comparative physiologists.

Section snippets

The beneficial acclimation hypothesis

One of the best examples of this new approach to physiological research has been the experimental analysis of the adaptive significance of physiological acclimation 8, 9, 10, 11, 12 (see Glossary). Traditionally, acclimation has been defined as the adjustment of physiological traits in response to changes in a single environmental variable in the lab [13], whereas acclimatization refers to physiological responses to environmental variables in the field [13]. Physiologists often assumed that all

Acclimation or developmental plasticity?

We suggest that the empirical studies discussed here are neither direct nor complete tests of the functional benefit of thermal acclimation, as defined from traditional physiological studies of acclimation. Rather, we suggest these studies are elegant analyses of the adaptive significance of developmental plasticity. Acclimation responses studied by traditional comparative physiologists differ substantially to the developmental plasticity examined by Leroi et al. [8], Bennett and Lenski [9] and

Exploring the BAH using competing hypotheses

In two additional studies exploring the BAH, both Huey and Berrigan [11] and Huey et al. [12] advocated a strong inference approach to examining questions relating to the thermal acclimation of ectotherms. Their approach involved testing among competing hypotheses that make different predictions as to how developmental temperature influences the thermal sensitivity of performance (Box 2).

Huey and Berrigan [11] and Huey et al. [12] then used the datasets of several previous studies, such as that

Conclusions and future directions

Previous empirical tests of the BAH have elegantly demonstrated the evolutionary significance of thermally induced developmental plasticity 8, 9, especially with the advent of a rigorous experimental design testing several competing hypotheses 11, 12. Importantly, these studies of the BAH have forcefully made the point that acclimation changes cannot just be assumed to be beneficial, but this is a hypothesis that must be rigorously tested. However, we believe that a detailed empirical

Acknowledgements

We thank Ian A. Johnston, Helga Guderley, Andy Clarke, Craig Moritz and Raoul Van Damme for stimulating discussions and/or reading the article. This article was improved substantially by comments from several anonymous referees. This work was supported by a small ARC grant awarded to C.E.F. and R.S.W. and a ARC Large Grant to C.E.F. and Craig Moritz.

Glossary

Acclimation
any facultative modification in a physiological trait in response to changes in an environmental variable in the lab. Changes can be in response to the developmental environment or long-term environmental shifts during the later stages of the life history of an organism (more traditionally studied). Responses can be beneficial, neutral or negative.
Acclimatization
facultative modifications in a physiological trait in response to changes in one or more environmental variables in the

References (28)

  • A.F. Bennett et al.

    Evolutionary adaptation to temperature: VI. Phenotypic acclimation and its evolution in Escherichia coli

    Evolution

    (1997)
  • A.A. Hoffmann

    Acclimation: increasing survival at a cost

    Trends Ecol. Evol.

    (1995)
  • R.B. Huey et al.

    Testing evolutionary hypotheses of acclimation

  • R.B. Huey

    Testing the adaptive significance of acclimation: a strong inference approach

    Am. Zool.

    (1999)
  • Cited by (289)

    View all citing articles on Scopus
    View full text