Genome composition predicts physiological response to environmental change in polyploid salamanders

Multi-trait analyses can be used to measure the differential performance of phenotypic traits in species complexes. Hybridization within these complexes can result in a mismatch between mitochondrial and nuclear DNA that may lead to reduced performance and acclimation capacity in hybrids. To test the effect of this mismatch on physiology, we compared physiological performance and acclimation capacity of metabolic rate (VCO2) and total resistance to water loss (rT) between two sexual Ambystoma species and a closely related unisexual lineage. We also separated unisexuals by their unique biotypes to determine how physiology varies with subgenomic composition. We found that unisexual biotypes exhibited phenotypes more like their related sexual species than to other unisexuals. We also found a trade-off between rT and VCO2, with increasing rT resulting in a decrease in VCO2. This trade-off was stronger in unisexuals than either sexual species, indicating that unisexuals may be more sensitive to environmental change. While we did not find evidence for mitonuclear mismatch, our results show that genomic composition of hybrids is more indicative of trait performance than other metrics (e.g., ploidy). Multi-trait analyses are imperative for understanding variation in phenotypic diversity, providing insight into how this diversity affects species responses to environmental change.