Evolutionary Dynamics of Gene Expression During Thermal Adaptation in Drosophila subobscura.

Global warming poses significant challenges to the persistence of biodiversity, requiring a deeper understanding of thermal adaptation, particularly at the genetic level. Examining gene expression changes offers critical insight into the molecular mechanisms driving adaptation, helping to identify which genes are activated or repressed during the adaptive dynamics. This study investigates the evolutionary dynamics of gene expression in Drosophila subobscura populations from different origins under progressive warming conditions. By analyzing transcriptomic changes across two generation gaps (after 9 and 23 generations of evolution), we found some complex evolutionary patterns of gene expression, including shifts from up to downregulation and vice versa, with the population of Dutch origin exhibiting greater variability in adaptive response than the population of Portuguese origin. Such complex dynamics involved enrichment of DNA replication-and DNA repair mechanisms in particular-in both sets of populations, although the timing and direction differed between them. We also found consistent downregulation of the immunity-related toll-NF-κB pathway in the replicated populations derived from the Dutch population. This study documents the dynamic and shifting nature of gene expression during adaptation to warming environments and highlights the critical role of population's history in shaping adaptive strategies. These findings deepen our understanding of the transcriptomic mechanisms driving thermal adaptation and provide a basis for predicting evolutionary responses to climate change.