Keeping pace with climate change: what is wrong with the evolutionary potential of upper thermal limits?

Authors

  • Mauro Santos,

    Corresponding author
    • Departament de Genètica i de Microbiologia, Grup de Biologia Evolutiva (GBE), Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
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  • Luis E. Castañeda,

    1. Departament de Genètica i de Microbiologia, Grup de Biologia Evolutiva (GBE), Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
    2. Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
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  • Enrico L. Rezende

    1. Departament de Genètica i de Microbiologia, Grup de Biologia Evolutiva (GBE), Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
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  • We acknowledge financial support from the Ministerio de Ciencia e Innovación, Spain (grant CGL2010-15395 to MS, JCI-2010-06156 fellowship to LEC, and grant BFU2009-07564 to ELR); from Generalitat de Catalunya (grant 2009SGR 636 to MS); and from the ICREA Acadèmia program.

Correspondence

Mauro Santos, Departament de Genètica i de Microbiologia, Facultat de Biociències, Edifici Cn, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain. Tel: +34 93 581 2725; Fax: +34 93 581 2387; E-mail: mauro.santos@uab.es

Abstract

The potential of populations to evolve in response to ongoing climate change is partly conditioned by the presence of heritable genetic variation in relevant physiological traits. Recent research suggests that Drosophila melanogaster exhibits negligible heritability, hence little evolutionary potential in heat tolerance when measured under slow heating rates that presumably mimic conditions in nature. Here, we study the effects of directional selection for increased heat tolerance using Drosophila as a model system. We combine a physiological model to simulate thermal tolerance assays with multilocus models for quantitative traits. Our simulations show that, whereas the evolutionary response of the genetically determined upper thermal limit (CTmax) is independent of methodological context, the response in knockdown temperatures varies with measurement protocol and is substantially (up to 50%) lower than for CTmax. Realized heritabilities of knockdown temperature may grossly underestimate the true heritability of CTmax. For instance, assuming that the true heritability of CTmax in the base population is h2 = 0.25, realized heritabilities of knockdown temperature are around 0.08–0.16 depending on heating rate. These effects are higher in slow heating assays, suggesting that flawed methodology might explain the apparently limited evolutionary potential of cosmopolitan D. melanogaster.

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