gene expression plasticity

The relationships between adaptive evolution, phenotypic plasticity, and canalization remain incompletely understood. Theoretical and empirical studies have made conflicting arguments on whether adaptive evolution may enhance or oppose the plastic response. Gene regulatory traits offer excellent potential to study the relationship between plasticity and adaptation, and they can now be studied at the transcriptomic level. Here we take advantage of three closely related pairs of natural populations of Drosophila melanogaster from contrasting thermal environments that reflect three separate instances of cold tolerance evolution. We measure the transcriptome-wide plasticity in gene expression levels and alternative splicing (intron usage) between warm and cold laboratory environments. We find that putatively adaptive changes in both gene expression and alternative splicing tend to neutralize the ancestral plastic response. Further, we test the hypothesis that adaptive evolution can lead to decanalization of the selected trait using inbreeding as a form of genetic perturbation. We indeed find strong evidence that putatively adaptive gene expression changes in cold-adapted populations show greater genetic decanalization than putatively neutral changes, but no clear support for this hypothesis for splicing traits.