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.,Effect of temperature fluctuations on male fitness traits in Drosophila birchiiThis Excel file contains 8 datasheets. Sheets 1-3 are for Experiments I ,II & III, containing information about transect, elevation of origin, isofemale line, focal male number and treatment. Data are for total cumulative offspring, number of matings and offspring per mating. Sheets 4-6 show wing centroid measurements for the same experiments respectively. Sheets 7-8 are summary line data for Experiments I and II used for heritability estimates and genetic correlations.Saxon et al_ data.xlsx,