Symbionts out of sync: decoupled physiological responses are widespread and ecologically important in lichen associations

A core vulnerability in symbioses is the need for coordination between the symbiotic partners, which are often assumed to be closely physiologically integrated. We critically re-examine this assumed integration in lichen symbioses, recovering a long overlooked yet fundamental physiological asymmetry in carbon balance. We examine the physiological, ecological and transcriptional basis of this asymmetry in the lichen Evernia mesomorpha. This carbon balance asymmetry depends on hydration source and aligns with climatic range limits. Differences in gene expression across the E. mesomorpha symbiosis suggest that the physiologies of the primary lichen symbionts are decoupled. Furthermore, we use gas-exchange data to show that asymmetries in carbon balance are widespread and common across evolutionarily disparate lichen associations. Using carbon balance asymmetry as an example, we provide evidence for the wide-ranging importance of physiological asymmetries in symbioses.

Methods
I. Ecophysiological data from measurements of Evernia mesomorpha, including gas-exchange datafiles, chlorophyll fluorescence imaging results, and associated supporting data (e.g. thallus masses and areas) and R script.

Thalli of Evernia mesomorpha (Boreal oak lichen) were exposed to hydration by water vapor alone or vapor followed by liquid water at a range of temperatures and light conditions. Data reports gas-exchange and chlorophyll fluorescence measurements of photosynthetic and respiratory activity in these different conditions.

II. Transcriptome data and analyses for Evernia mesomorpha

Thalli of Evernia mesomorpha (Boreal oak lichen) were exposed to hydration by water vapor alone or vapor followed by liquid water. RNA was extracted for transcriptome analysis, this set of data includes raw data and progressive processing datasets, as well as code.

III. Ecophysiological data from measurements across 42 species

Thalli of a wide range of lichen taxa were to hydration by water vapor alone or vapor followed by liquid water. Data reports summarized gas-exchange measurements of photosynthetic and respiratory activity, as well as associated categorical traits for these taxa.