DOI: 10.5061/dryad.wh70rxwrv
title: Data from: Shifting effects of host physiological condition following pathogen establishment

description: Understanding host persistence with emerging pathogens is essential for
 conserving populations. Hosts may initially survive pathogen invasions
 through pre-adaptive mechanisms. However, whether pre-adaptive traits are
 directionally selected to increase in frequency depends on the
 heritability and environmental dependence of the trait and the costs of
 trait maintenance. Body condition is likely an important pre-adaptive
 mechanism aiding in host survival, although it can be seasonally variable
 in wildlife hosts. We used data collected over seven years on bat body
 mass, infection, and survival to determine the role of host body condition
 during the invasion and establishment of the emerging disease, white-nose
 syndrome. We found that when the pathogen first invaded, bats with higher
 body mass were more likely to survive, but this effect dissipated
 following the initial epizootic. We also found that heavier bats lost more
 weight over winter, but fat loss depended on infection severity. Lastly,
 we found mixed support that bat mass increased in the population after
 pathogen arrival; high annual plasticity in individual bat masses may have
 reduced the potential for directional selection. Overall, our results
 suggest that some factors that contribute to host survival during pathogen
 invasion may diminish over time, and are potentially replaced by other
 host adaptations.
description: We studied the arrival and establishment of <em>P.
 destructans </em>at 24 hibernacula (caves and mines where bats spend
 the winter) in Virginia, Wisconsin, Illinois, and Michigan over seven
 years (Tables S1–S3). We visited sites twice per winter and collected data
 on infection status and body mass of bats. At each site, we sampled
 individual bats (Table S1, mean = 9.2, range: 1–50) stratified across site
 sections. Because sites used in this study were primarily small mines
 where it was possible to observe all bats present, in many instances, all
 individuals in the population were sampled. For each bat, we collected a
 standardized epidermal swab sample (Langwig et al. 2015 Proceedings B),
 attached a unique aluminum band, and measured body mass using a digital
 scale (GDealer, accuracy +/- 0.03 grams). Because common condition indices
 are no more effective than body mass for estimating fat stores, we did not
 include information on bat forearm size in order to reduce handling
 disturbance. At every visit, we recorded and resampled any previously
 banded bats present. We stored swabs in RNAlater, and samples were kept at
 0 C while in the field, and then at -20 C until processing. We tested
 samples for <em>P. destructans </em>DNA using real-time PCR
 and quantified fungal loads (Muller et al. 2013 Mycologia). Animal
 handling protocols were approved by Virginia Tech IACUC (#17-180,
 #20-150). We investigated the effect of bat early
 hibernation (November) body mass on the probability an individual was
 recaptured overwinter (e.g. within-winter) using a generalized linear
 mixed model (GLMM) with a binomial distribution and a probit link, with
 site as a random effect, and body mass and disease phase (epidemic = 1–3
 years since pathogen arrival, or established = 4–7 years since pathogen
 arrival) as interacting fixed effects (Table S1, total N individuals =
 775). Phases were established based on previous results demonstrating that
 populations approach stability by year 4 following WNS arrival. For
 analyses of individual survival and body mass, results were similar
 whether we used categorical disease phase or years since WNS as a
 continuous variable (Appendix) and grouping by phase maximized the number
 of bats in the epidemic years when mortality was high and the number of
 recaptured bats was low. For bats that were recaptured overwinter, we
 examined the effect of early winter body mass and infection on the amount
 of mass lost overwinter during both the epidemic and established phase
 using a linear mixed model with site as a random effect and the change in
 body mass as the response variable and fixed effects of early winter mass
 interacting early winter fungal loads with additional additive effect of
 disease phase (Table S2, total N=158). Finally, we explored changes in
 mass over time since the invasion of <em>P. destructans</em>
 on an individual and population level to examine both plasticity and
 phenotypic change. For bats that were recaptured in multiple years, we
 used a linear mixed model with mass as a response variable, years since
 WNS as a fixed effect, and bat band ID as a random effect to explore
 plasticity in whether individual bat mass changed over time (N=91
 observations, 42 unique bands, 1–3 recapture events per bat, Appendix
 4.0.3). At a population level, declines in sites with the best invasion
 mass data limited our ability to explore changes in mass, so we restricted
 our analyses to N=5 sites (Table S3) that were measured during invasion
 and had sufficient bats to estimate during established periods using
 log<sub>10</sub> mass as our response variable (logged to
 normalize) and years since WNS interacting with season with site as a
 random effect. All analyses were conducted in R v.4.1.2 using
 lme4.
description: No special programs are required to open the data files.