Anthropogenic climate change has led to unprecedented shifts in
temperature across many ecosystems. In a context of rapid environmental
changes, acclimation is an important process as it may influence the
capacity of organisms to survive under novel thermal conditions.
Mechanisms of acclimation could involve upregulation of stress response
genes involved in protein folding, DNA damage repair and the regulation
of signal transduction genes, along with a simultaneous downregulation
of genes involved in growth or cell cycle, in order to maintain cellular
functions and equilibria. We transplanted Lobaria pulmonaria lichens
originating from different forests to determine the relative effects of
long-term acclimation and genetic factors on the variability in
expression of mycobiont and photobiont genes. We found a strong response
of mycobiont and photobiont to high temperatures, regardless of sample
origin. The green-algal photobiont had an overall lower response than
the mycobiont. The gene expression of both symbionts was also influenced
by acclimation to transplantation sites and by genetic factors. Lobaria
pulmonaria seems to have evolved powerful molecular pathways to deal
with environmental fluctuations and stress and can acclimate to new
habitats by transcriptomic convergence. Although L. pulmonaria has the
molecular machinery to counteract short-term thermal stress, survival of
lichens like L. pulmonaria depends mostly on their long-term positive
carbon balance, which can be compromised by warmer temperatures and
reduced precipitation, and both these outcomes have been predicted for
Central Europe in connection with global climate change