Climate change and unequal phenological changes across four trophic levels: constraints or adaptations?

Authors

  • Christiaan Both,

    Corresponding author
    1. Animal Ecology Group, Center for Ecological and Evolutionary Studies, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands;
      Correspondence author. E-mail: c.both@rug.nl
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  • Margriet Van Asch,

    1. Netherlands Institute of Ecology (NIOO-KNAW), PO Box 40, 6666 ZG Heteren, The Netherlands; and
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  • Rob G. Bijlsma,

    1. Animal Ecology Group, Center for Ecological and Evolutionary Studies, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands;
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  • Arnold B. Van Den Burg,

    1. Bargerveen Foundation/Department of Animal Ecology, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands
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  • Marcel E. Visser

    1. Netherlands Institute of Ecology (NIOO-KNAW), PO Box 40, 6666 ZG Heteren, The Netherlands; and
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Correspondence author. E-mail: c.both@rug.nl

Summary

  • 1Climate change has been shown to affect the phenology of many organisms, but interestingly these shifts are often unequal across trophic levels, causing a mismatch between the phenology of organisms and their food.
  • 2We consider two alternative hypotheses: consumers are constrained to adjust sufficiently to the lower trophic level, or prey species react more strongly than their predators to reduce predation. We discuss both hypotheses with our analyses of changes in phenology across four trophic levels: tree budburst, peak biomass of herbivorous caterpillars, breeding phenology of four insectivorous bird species and an avian predator.
  • 3In our long-term study, we show that between 1988 and 2005, budburst advanced (not significantly) with 0·17 d yr−1, while between 1985 and 2005 both caterpillars (0·75 d year−1) and the hatching date of the passerine species (range for four species: 0·36–0·50 d year−1) have advanced, whereas raptor hatching dates showed no trend.
  • 4The caterpillar peak date was closely correlated with budburst date, as were the passerine hatching dates with the peak caterpillar biomass date. In all these cases, however, the slopes were significantly less than unity, showing that the response of the consumers is weaker than that of their food. This was also true for the avian predator, for which hatching dates were not correlated with the peak availability of fledgling passerines. As a result, the match between food demand and availability deteriorated over time for both the passerines and the avian predators.
  • 5These results could equally well be explained by consumers’ insufficient responses as a consequence of constraints in adapting to climate change, or by them trying to escape predation from a higher trophic level, or both. Selection on phenology could thus be both from matches of phenology with higher and lower levels, and quantifying these can shed new light on why some organisms do adjust their phenology to climate change, while others do not.

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