DOI: 10.5061/dryad.481g3
title: Data from: Physical calculations of resistance to water loss improve predictions of species range models

description: Species ranges are constrained by the physiological tolerances of
 organisms to climatic conditions. By incorporating physiological
 constraints, species distribution models can identify how biotic and
 abiotic factors constrain a species’ geographic range. Rates of water loss
 influence species distributions, but characterizing water loss for an
 individual requires complex calculations. Skin resistance to water loss
 (ri) is considered to be the most informative metric of water loss rates
 because it controls for experimental biases. However, calculating ri
 requires biophysical equations to solve for the resistance of the air that
 surrounds an organism, termed the boundary layer resistance (rb). Here, we
 compared theoretical and empirical methods for measuring skin resistance
 to water loss of a Plethodon salamander collected from nature. For the
 empirical methods, we measured rb of agar replicas at five body sizes, two
 temperatures, three vapor pressure deficits, and six flow rates using a
 flow through system. We also calculated rb using biophysical equations
 under the same experimental conditions. We then determined the ecological
 implications of incorporating skin and boundary layer resistance into a
 species range model that estimated potential activity time and energy
 balance throughout the geographic range of the study species. We found
 that empirical methods for calculating rb resulted in negative values of
 ri, whereas biophysical calculations produced meaningful values of ri. The
 species range model determined that ignoring realistic boundary layer and
 skin resistances reduced average estimates of energy balance by as much as
 64% and potential activity time by 88% throughout the spatial extent of
 the model. We conclude that the use of agar replicas is an inadequate
 technique to characterize skin resistance to water loss, and incorporating
 boundary layer and skin resistances to water loss improve estimates of
 activity and energetics for mechanistic species distribution models. More
 importantly, our study suggests incorporating the physical processes
 underlying rates of water loss could improve estimates of habitat
 suitability for many animals.
description: Empirical vs theoretical
 skin resistancesThis file contains the
 raw data of skin resistances calculated from theoretical and empirical
 methods.fig1_empirical_vs_theoretical.xlsxEmpirical vs theoretical estimates of the boundary layer vs flow ratefig2_rb_flow_rate.xlsxEmpirical vs theoretical estimates of the boundary layer vs VPDfig3_vpd_rb.xlsxEstimates of activity and energy balance with and without the boundary layerfig5_energy_and_activity_with_rb.xlsxPositive or negative energy balance against VPDvpd_energy_balance.xlsxSkin resistance values across taxafig7_rs_comparative.xlsxPython code for biophysical modelThis code requires hourly temperature and VPD ascii files. It will compile each file individually and calculate estimates of activity and energy for a single night. This program should not be used for monthly or yearly estimates of activity and net energy balance unless a user has provided substantial modifications.biophysical_model.pyActivity without realistic resistances to water lossEstimates of activity (in seconds) without a boundary layer or realistic skin resistance to water loss over a single night in August.activity_norb_rs1.ascActivity with realistic resistancesEstimates of activity (seconds) with a boundary layer and average skin resistance (5 sec/cm) over a single night in August.activity_rb_rs5.ascEnergy without realistic resistancesNet energy balance (J) without a boundary layer or realistic skin resistance to water loss over a single night in August.energy_norb_rs1.ascEnergy with realistic resistances to water lossNet energy balance (J) with realistic resistance to water loss and skin resistance to water loss over a single night in August.energy_rb_rs5.asc