Many expressions of phenotype, such as physiological performance, integrate multiple underlying traits to function. Linking component traits to adaptive physiology thus gives insight into mechanisms of selection acting on performance. Genome size (C-value) is a trait that influences physiology in multiple taxa by exerting a nucleotypic effect, constraining cell size and cellular physiology such that whole-organism mass-specific metabolism is reduced with increasing C-value. We tested for this mechanism of C-value function acting in lungless salamanders, plus an unexplored potential mechanism of C-value effects constraining water transport across the body surface to influence cutaneous water loss rates. We found no evidence for a nucleotypic effect on metabolic rates, but we demonstrate a relationship between C-value and water loss physiology. Under warmer experimental conditions, C-value was inversely correlated with water loss and positively correlated with resistance to water loss, which demonstrated adaptive plasticity at higher temperatures. We hypothesize this pattern results from differences in cell size constraining diffusion and evaporation of water from the skin under warm conditions when cutaneous perfusion is reduced. Testing this hypothesis may confirm a previously unappreciated adaptive role for C-value variation in this group, and reveals the possibility that genome size influences physiological exchange across transport barriers more broadly.

README_Johnson_JEB.txt : readme file with detailed information on all data files

Johnson_JEB_physiol.csv : Raw, untransformed data for all morphological and physiological measurements from each individual experiment trial.

Johnson_JEB_phydat.csv : Species mean values for morphological predictors, physiological responses, and species climate profiles under different experimental treatments. All morphological and physiological values are natural-log transformed.

Johnson_JEB_r10.csv : R10 values calculated for each species under different experimental treatments.

Johnson_JEB_supplement2.xlsx : Additional supplementary summary tables. Includes model comparisons, allometry variance analysis, path model coefficients, and GenBank accession numbers used in phylogeny construction. Table descriptions within the file. 

Johnson_JEB_Pleth60.con.tre : Nexus format 60-species consensus phylogeny of North American plethodontidae, direct output from MrBayes v3.2.7. Used to accurately construct broad phylogenetic relationships among focal species under analysis. 

Johnson_JEB_Pleth09_trimmed.con.tre : Tree format 8-species phylogeny used in all comparative analyses, trimmed from the 60-species MrBayes consensus phylogeny.