Assessing hybrid vigor using the thermal sensitivity of physiological trade-offs in tiger salamanders

Hybridization between species affects biodiversity and population sustainability in numerous ways, many of which depend on the fitness of the hybrid relative to the parental species. Hybrids can exhibit fitter phenotypes compared to the parental lineages, and this ‘hybrid vigor’ can then lead to the extinction of one or both parental lines.
In this study, we analyzed the relationship between water loss and gas exchange to compare physiological performance among three tiger salamander genotypes – the native California tiger salamander (CTS), the invasive barred tiger salamanders (BTS), and CTS x BTS hybrids across multiple temperatures (13.5°C, 20.5°C, and 23.5°C). We developed a new index of performance, the water-gas exchange ratio (WGER), which we define as the ratio of gas exchange to evaporative water loss (µL VO2/µL H2O). The ratio describes the ability of an organism to support energetically costly activities with high levels of gas exchange while simultaneously limiting water lo..., , , # Assessing hybrid vigor using the thermal sensitivity of physiological trade-offs in tiger salamanders

## Description of the data and file structure

**Tiger\_salamander\_phys\_data.csv**
This data includes the metabolic rate [vo2 (uL\*h-1)], resistance to water loss [resistance (s\*cm-1)], and water-gas exchange ratio [wger (uL\*hr-1 vco2 / uL\*hr-1 evaporative water loss)] of all salamanders. Other data in this file include the salamander ID assigned to individuals (ID), the genotype of each individual [genotype - hybrid, barred tiger salamander (BTS), and California tiger salamander (CTS)], the temperature treatment at which that individual was measured [temperature (°C)], and the mass of the salamander prior to experiments [mass (g)]. Methods for collecting the above data are described in the manuscript.

**Tiger\_salamander\_phys\_analysis.R**
This file includes the R script used to conduct all analyses and create all figures presented in this study using the above dataset.