Supplementary data for: Effects of thermal acclimation on the proteome of the planarian Crenobia alpina from an alpine freshwater spring

Species' acclimation capacities and their ability to maintain molecular homeostasis outside of ideal temperature ranges will partly predict their success following climate-change induced thermal regime shifts. Theory predicts that ectothermic organisms from thermally stable environments have muted plasticities, and that these species may be particularly vulnerable to temperature increase. Whether such species retained or lost acclimation capacities remains largely unknown. We studied proteome changes in the planarian Crenobia alpina, a prominent member of cold-stable alpine habitats that is considered to be cold-adapted stenotherm. We found that the species' CT_max is above its experienced habitat temperatures and that different populations exhibit differential CTmax acclimation capacities, whereby an alpine population showed reduced plasticity. In a separate experiment, we acclimated C. alpina individuals from the alpine population to 8, 11, 14, or 17°C over the course of 168 h and compared a comprehensively annotated species-specific proteome. Network analyses of 3399 proteins and protein set enrichment show that while the species' proteome is overall stable across these temperatures, protein sets functioning in oxidative stress response, mitochondria, protein synthesis and turnover are lower abundant following warm acclimation. Proteins associated with an unfolded protein response, ciliogenesis, tissue damage repair, development, and the innate immune system were higher abundant following warm acclimation. Our findings suggest that this species has not suffered DNA decay (e.g., loss of heat-shock proteins) during evolution in a cold-stable environment and retained plasticity in response to elevated temperatures, challenging the notion that stable environments necessarily result in muted plasticity.