QUANTITATIVE GENETIC DIVERGENCE AND STANDING GENETIC (CO)VARIANCE IN THERMAL REACTION NORMS ALONG LATITUDE

Authors

  • David Berger,

    1. Institute of Evolutionary Biology and Environmental Studies, University of Zurich, CH-8057 Zurich, Switzerland
    2. Animal Ecology at Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, SE-75236 Uppsala, Sweden
    Search for more papers by this author
  • Erik Postma,

    1. Institute of Evolutionary Biology and Environmental Studies, University of Zurich, CH-8057 Zurich, Switzerland
    Search for more papers by this author
  • Wolf U. Blanckenhorn,

    1. Institute of Evolutionary Biology and Environmental Studies, University of Zurich, CH-8057 Zurich, Switzerland
    Search for more papers by this author
  • Richard J. Walters

    1. Institute of Evolutionary Biology and Environmental Studies, University of Zurich, CH-8057 Zurich, Switzerland
    2. School of Biological Sciences, University of Reading, Reading, United Kingdom
    Search for more papers by this author

Abstract

Although the potential to adapt to warmer climate is constrained by genetic trade-offs, our understanding of how selection and mutation shape genetic (co)variances in thermal reaction norms is poor. Using 71 isofemale lines of the fly Sepsis punctum, originating from northern, central, and southern European climates, we tested for divergence in juvenile development rate across latitude at five experimental temperatures. To investigate effects of evolutionary history in different climates on standing genetic variation in reaction norms, we further compared genetic (co)variances between regions. Flies were reared on either high or low food resources to explore the role of energy acquisition in determining genetic trade-offs between different temperatures. Although the latter had only weak effects on the strength and sign of genetic correlations, genetic architecture differed significantly between climatic regions, implying that evolution of reaction norms proceeds via different trajectories at high latitude versus low latitude in this system. Accordingly, regional genetic architecture was correlated to region-specific differentiation. Moreover, hot development temperatures were associated with low genetic variance and stronger genetic correlations compared to cooler temperatures. We discuss the evolutionary potential of thermal reaction norms in light of their underlying genetic architectures, evolutionary histories, and the materialization of trade-offs in natural environments.

Ancillary