# Genetic background and thermal regime influence adaptation to novel environment in the seed beetle, Callosobruchus maculatus [https://doi.org/10.5061/dryad.f1vhhmgz7](https://doi.org/10.5061/dryad.f1vhhmgz7) The data contained in these two data files (bodymass.csv and lifehistory.csv) contain data on body mass, development time, lifetime reproductive success, and age-specific reproduction of two populations of *Callosobruchus maculatus* that evolved under fluctuating or constant thermal regimes and were subsequently assayed under fluctuating or thermal regimes. ## Description of the data and file structure bodymass.csv contains information on: * Pop: Population (either USA or LEIC). * Treatment: Note that C = Constant Regime Constant Environment; I = Fluctuating Regime Fluctuating Environment; CIA = Constant Regime Fluctuating Environment; ICA = Fluctuating Regime Constant Environment. The transformation for this occurs in the code. * Rep: Replicate number. * Sex: Sex of individual (M or F). * Day: Always 22. * VCMass: Chamber mass (g). * VCBeet.Mass: Chamber w/ beetle (g). * Beet.Mass: Beetle mass (g). lifehistory.csv contains information on: * Pop: Population (either USA or LEIC). * Treat: Treatment; note that C = Constant Regime Constant Environment; I = Fluctuating Regime Fluctuating Environment; CIA = Constant Regime Fluctuating Environment; ICA = Fluctuating Regime Constant Environment. The transformation for this occurs in the code. * Rep: Replicate. * Pair.Date: Date paired. * VC: Chamber ID. * DayEgg: Egg day. * DateEgg: Date of first egg lay. * DateMeasure: Date of measurement for offspring. * DT: Development Time. * Males/Female/Total: Number of offspring that are Male/Female/Combined Total. * Comments: Comments made during data collection. ## Code/Software Code used to run the analysis and produce the graphs is located on GitHub via https://github.com/EIvimeyCook/Fluctuating\_Beetles or via Zenodo with the DOI, https://zenodo.org/doi/10.5281/zenodo.10118422.

Climate change is associated with the increase in both mean and variability of thermal conditions. Therefore, the use of more realistic fluctuating thermal regimes is the most appropriate laboratory method for predicting population responses to thermal heterogeneity. However, the long- and short-term implications of evolving under such conditions are not well understood. Here, we examined differences in key life history traits among populations of seed beetles (Callosobruchus maculatus) that evolved under either constant control conditions or in an environment with fluctuating daily temperatures. Specifically, individuals from two distinct genetic backgrounds were kept for 19 generations at one of two temperatures, a constant temperature (T=29°C) or a fluctuating daily cycle (Tmean=33°C, Tmax=40°C, and Tmin=26°C), and were assayed either in their evolved environment or in the other environment. We found that beetles that evolved in fluctuating environments but were then switched to constant 29°C conditions had far greater lifetime reproductive success compared to beetles that were kept in their evolved environments. This increase in reproductive success suggests that beetles raised in fluctuating environments may have evolved greater thermal breadth than control condition beetles. In addition, the degree of sexual dimorphism in body size and development varied as a function of genetic background, evolved thermal environment, and current temperature conditions. These results highlight not only the value of incorporating diel fluctuations into climate research but also suggest that populations that experience variability in temperature may be better able to respond to both short- and long-term changes in environmental conditions.