Conceptualising the evolutionary quantitative genetics of phenological life history events: breeding time as a plastic threshold trait

Jane Reid* (Corresponding Author), Paul Acker

*Corresponding author for this work

Research output: Contribution to journalComment/debatepeer-review


Successfully predicting adaptive phenotypic responses to environmental changes, and predicting resulting population outcomes, requires that additive genetic (co)variances underlying micro-evolutionary and plastic responses of key traits are adequately estimated on appropriate quantitative scales. Such estimation in turn requires that focal traits, and their underlying quantitative genetic architectures, are appropriately conceptualised. Here, we highlight that directly analysing observed phenotypes as continuously distributed quantitative traits can potentially generate biased and misleading estimates of additive genetic variances and individual-by-environment and gene-by-environment interactions, and hence of forms of plasticity and genetic constraints, if in fact the underlying biology is best conceptualised as an environmentally-sensitive threshold trait. We illustrate this scenario with particular reference to the key phenological trait of seasonal breeding date, which has become a focus for quantifying joint micro-evolutionary, plastic and population responses to environmental change, but has also become a focus for highlighting that predicted adaptive outcomes are not always observed. Specifically, we use simple simulations to illustrate how potentially misleading inferences on magnitudes of additive genetic variance, and forms of environmental interactions, can arise by directly analysing observed breeding dates if the transition to breeding in fact represents a threshold trait with latent-scale plasticity. We summarise how existing and new datasets could be (re)analysed, potentially providing new insights into how critical micro-evolutionary and
plastic phenological responses to environmental variation and change can arise and be constrained.
Original languageEnglish
JournalEvolution Letters
Publication statusAccepted/In press - 30 Jan 2022


  • Additive genetic variance
  • breeding date
  • gene-by-environment interaction
  • phenology
  • phenotypic plasticity
  • quantitative genetics
  • reaction norm
  • threshold trait


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