Experimental evolution in Drosophila uncovers the importance of phenotypic plasticity and canalization for the evolution of gene expression in a changed environment. Christian W. Schloetterer¹, Miguel Gallach^1,2, Viola Nolte¹, Pablo Orozco-TerWengel^1,3, Eszter Ari¹. 1) Inst f Populationsgenetik, Vetmeduni Vienna, Wien, Austria; 2) present address: Center for Integrative Bioinformatics Vienna, Max F. Perutz Laboratories, University of Vienna and Medical University of Vienna. Vienna, Austria; 3) present address: Cardiff University, Wales, UK.

   The evolutionary forces shaping gene expression divergence are still poorly understood. Gene expression divergence between natural populations in their native environment is determined by non-genetic (i.e., plastic) and genetic (i.e., potentially adaptive) factors. Their relative importance can be determined by measuring gene expression of natural populations evolved in different environments but assayed under the same conditions (i.e., common garden experiments). Here, we analyze patterns of gene expression in experimental populations that have evolved for one year under temperate and tropical temperature regimes in the laboratory. Our results show that plasticity contributes much more (up to 66 % of the total expressed genes) than genetic change (7 %) to temperature-specific gene expression patterns. This suggests that plasticity in gene expression is more important for the short term response to a novel environment (i.e., temperature regime). Both evolved populations showed more variability in gene expression among replicates when they were cultivated in a non-native environment rather than their native one. This transcriptome-wide decanalization of gene expression in non-native environments demonstrates how non-selective forces contribute to gene expression divergence, raising the question to what extent environmental heterogeneity needs to be considered for the interpretation of inter- and intra-specific patterns of gene expression evolution.