Abstract 1834 Environmental change determines selection for transcriptional plasticity in ectotherms

Phenotypic plasticity, expression of a genotype in different environments, can either support adaptation (i.e. adaptive plasticity) and oppose it (i.e. maladaptive plasticity). Recent studies suggest that differences in plastic gene expression among recently derived or geographically variable populations are primarily driven by selection against maladaptive plasticity. However, it is unclear whether and how these patterns extend across taxa or for different scopes of environmental change. I will discuss two cases on transcriptional plasticity: one on long-term species differentiation and another on rapid adaptation to combined environmental stressors. For the former, I will compare global differential gene expression (DGE) patterns for species of temperate and tropical Drosophila with evolved differences in thermal tolerance. For the latter, I will compare DGE patterns for artificially selected marine zooplankton that adapted to future ocean warming and acidification (OWA) environments. The results for the Drosophila experiments indicate that increased transcriptional plasticity promotes adaptation to cold environments. For cold-adapted species, transcriptional plasticity at cold-stress temperatures is driven by more gene categories that are not conserved across species than one would expect by chance. By contrast, the adaptation to OWA environments reduces transcriptional plasticity relative to lineages that never experienced OWA. This reduction is accompanied by a corresponding reduction in allelic diversity for OWA-selected lineages when they experience previously benign, ancestral environments. Moreover, this reduction in transcriptional plasticity is accompanied by fitness consequences. Together, these results suggest that transcriptional plasticity can be adaptive on evolutionary timescales, but maladaptive after rapid adaptation to costly stress. As climate conditions continue to change, the results from these studies indicate that the evolution of transcriptional plasticity may present adaptive strategies to manage stressful thermal environments. This work was funded by the National Science Foundation (NSF) and the National Oceanic and Atmospheric Association (NOAA).