Data from: Temperature fluctuations during development reduce male fitness and may limit adaptive potential in tropical rainforest Drosophila

Understanding the potential for organisms to tolerate thermal stress
through physiological or evolutionary responses is crucial given rapid
climate change. Although climate models predict increases in both
temperature mean and variance, such tolerances are typically assessed
under constant conditions. We tested the effects of temperature
variability during development on male fitness in the rainforest fly
Drosophila birchii, by simulating thermal variation typical of the warm
and cool margins of its elevational distribution, and estimated
heritabilities and genetic correlations of fitness traits. Reproductive
success was reduced for males reared in warm (mean 24°C) fluctuating (±
3°C) versus constant conditions but not in cool fluctuating conditions
(mean 17°C), although fluctuations reduced body size at both temperatures.
Male reproductive success under warm fluctuating conditions was similar to
that at constant 27°C, indicating that briefly exceeding critical thermal
limits has similar fitness costs to continuously stressful conditions.
There was substantial heritable variation in all traits. However,
reproductive success traits showed no genetic correlation between
treatments reflecting temperature variation at elevational extremes, which
may constrain evolutionary responses at these ecological margins. Our data
suggest that even small increases in temperature variability will threaten
tropical ectotherms living close to their upper thermal limits, both
through direct effects on fitness and by limiting their adaptive
potential.