Data and code from: Climatic origin and plasticity shape emergence timing and fitness in bees and wasps under experimental climate regimes

Climate warming threatens the persistence of insect populations by forcing
them to adjust their phenology—responses that may be constrained by local
adaptation and involve physiological trade-offs. We investigated how
hymenopterans with contrasting seasonal phenology and from different
climates adjust their emergence timing under current and projected future
climates. We also examined the consequences of these adjustments on body
mass at emergence as a key fitness trait. We analysed the emergence timing
of 14,921 individuals from five cavity-nesting bee and wasp species
exposed to cold, warm, and hot post-winter temperature treatments in a
common garden experiment to identify potential genotype-environment
interactions. Insects had developed at 161 sites of origin across southern
Germany, covering multi-annual mean temperatures (MAT) of 5.9 to 10 ºC and
differing in the temperature deviation (ΔT) that insects experienced
during development in the pre-emergence year relative to MAT. Emergence
timing was highly plastic to post-winter temperatures, with insects
emerging earlier in warmer treatments. However, emergence was modulated by
MAT and ΔT, suggesting genetic adaptation to long-term climatic conditions
and adjustments to short-term temperature deviations. For spring-emerging
species, individuals from sites with higher MAT and warmer treatments
emerged the earliest (cogradient variation). In contrast, the latest
summer-emerging species exhibited countergradient variation: in the cold
treatment, individuals from higher MAT emerged later than those from lower
MAT. In spring species, mass loss was higher in warmer post-winter
treatments, with the strongest reductions observed in cool-adapted
individuals. Mass loss was particularly rapid for summer females in warmer
treatments, with individuals emerging later losing up to 34 % of their
mass. However, body mass of summer insects was independent of MAT and ΔT.
Our results demonstrate high plasticity of cavity-nesting Hymenoptera to
post-winter temperatures but also suggest that local adaptation and
responses to early-life temperature can compromise fitness under rapid
climate changes. This large-scale experimental study highlights the
complex drivers of insect emergence phenology and fitness and suggests
that cool-adapted, spring-emerging species may be most vulnerable to
ongoing climate warming.