Data from: Phenological mismatch drives selection on elevation, but not on slope, of breeding time plasticity in a wild songbird

Phenotypic plasticity is an important mechanism for populations to respond
to fluctuating environments, yet may be insufficient to adapt to a
directionally changing environment. To study whether plasticity can evolve
under current climate change, we quantified selection and genetic
variation in both the elevation (RNE) and slope (RNS) of the breeding time
reaction norm in a long-term (1973–2016) study population of great tits
(Parus major). The optimal RNE (the caterpillar biomass peak date
regressed against the temperature used as cue by great tits) changed over
time, whereas the optimal RNS did not. Concordantly, we found strong
directional selection on RNE, but not RNS, of egg-laying date in the
second third of the study period; this selection subsequently waned,
potentially due to increased between-year variability in optimal laying
dates. We found individual and additive genetic variation in RNE but,
contrary to previous studies on our population, not in RNS. The predicted
and observed evolutionary change in RNE were, however, marginal, due to
low heritability and the sex limitation of laying date. We conclude that
adaptation to climate change can only occur via micro-evolution of RNE,
but this will necessarily be slow and potentially hampered by increased
variability in phenotypic optima.