Data from: Mild warming induces divergent plastic responses in gene expression among populations of a temperate butterfly

In response to potentially stressful conditions, for example, due to climate change, organisms can move, adjust through phenotypic plasticity, and evolve. Evolution can act on mean trait values, but also on plasticity itself. We performed a common garden experiment with two populations of Glanville fritillary butterflies originating from different latitudes in Europe, each tested at two temperature treatments. We investigated gene expression patterns using differential expression analysis as well as weighted gene co-expression network analysis (WGCNA) to disentangle genetic from plastic effects. We found that, regardless of population of origin, most differentially expressed genes were responsive to temperature. We also found strong evidence for variation in plasticity between populations (GxE), but no clear evidence for genetic assimilation or compensation. Patterns for gene co-expression modules were more complex, indicating the importance of considering coordinated, low-level changes across many genes. Biological processes overrepresented in differentially expressed genes and gene co-expression modules are generally related to cellular maintenance and growth. Our results highlight the importance of intraspecific differences in phenotypic plasticity in response to mild warming.