Growth-dependent acclimation constrains climatic response for the lichen epiphyte Lobaria pulmonaria

Abstract

Abstract Species can respond to climate change by migrating to track their suitable climate space, and/or through adaptation (across generations) or acclimation (by individuals) to a changed in situ environment. Lichens provide an excellent model for studying acclimation; being poikilohydric, there is strong evidence that their phenotype presents an adaptation to different moisture regimes, and that key aspects of the phenotype, notably specific thallus mass (STM), have plasticity towards effective acclimation that maximizes water storage in drier environments. In this study we quantified acclimation of STM for Lobaria pulmonaria across a regional climatic gradient, and within sites for different microclimates, using a one-year common garden growth experiment. We found that STM tended to increase with thallus growth; however, when accounting for growth, STM shifted to be lower than average in wetter environments, higher than average in intermediate environments, and failed to respond in the driest environment where growth was compromised. The possibility of phenotypic acclimation in Lobaria pulmonaria appears to be functionally linked to the propensity for growth, and we present a scheme coupling growth with STM to define the limits of the species realized niche.