Long‐term exposure to an invasive fungal pathogen decreases Eptesicus fuscus body mass with increasing latitude

Abstract

Invasive pathogens threaten wildlife health and biodiversity. Physiological responses of species highly susceptible to pathogen infections following invasion are well described. However, the responses of less susceptible species (relative to highly susceptible species) are not well known. Latitudinal gradients, which can influence body condition via Bergmann's rule and/or reflect the time it takes for an introduced pathogen to spread geographically, add an additional layer for how mammalian species respond to pathogen exposure. Our goal was to understand how hosts less susceptible to pathogen infections respond to long-term pathogen exposure across a broad latitudinal gradient.We examined changes in body mass throughout pathogen exposure time across the eastern United States (latitude ranging 30.5 N-44.8 N) in Eptesicus fuscus, a bat species classified as less susceptible to infection (relative to highly susceptible species) by the invasive fungal pathogen that causes white-nose syndrome, Pseudogymnoascus destructans (Pd). Using 30 years of spring through fall adult capture records, we created linear mixed-effects models for female and male bats to determine how mass or mass variation changed across the eastern United States from pre-Pd invasion years through Pd invasion (0-1 years with Pd), epidemic (2-4 years with Pd), and established years (5+ years with Pd). By Pd establishment, all female and male bats decreased body mass with increasing latitude across a spatial threshold at 39.6 N.Differences in bat mass north and south of the spatial threshold progressively increased over Pd exposure time-steps such that body mass was lower in northern latitudes compared to southern latitudes by Pd establishment.Results indicated that the progressive differences in E. fuscus body mass with latitude across the eastern United States are due to long-term pathogen exposure; however, other environmental and ecological pressures may contribute to decreases in E. fuscus body mass with latitude and long-term pathogen exposure. As pathogen introductions and emerging infectious diseases become

Long-term spring through fall capture data of Eptesicus fuscus in the eastern USA before and after white-nose syndrome

“…Therefore, the year of Pd introduction was set at ‘0’, with negative integers representing years prior to Pd introduction and positive integers representing years following Pd introduction within each state of capture. From this variable (“years_Pd”), we created another variable (“disease_time_steps”) categorizing pathogen occurrence timing into invasion time-steps [3 , 12 , 20] . These time-steps included pre-invasion years (< 0 years since Pd introduction), invasion years (0 – 1 years since Pd introduction), epidemic years (2 – 4 years since Pd introduction) and established years (5 + years since Pd introduction).…”

“…These time-steps included pre-invasion years (< 0 years since Pd introduction), invasion years (0 – 1 years since Pd introduction), epidemic years (2 – 4 years since Pd introduction) and established years (5 + years since Pd introduction). We used these time-steps to remain consistent with pathogen occurrence time groups within the white-nose syndrome literature [3 , 12] , in lieu of unavailable pathogen prevalence data.…”

“…Here, we provide a description of a dataset representing 30 years of E. fuscus spring through fall capture data across 11 eastern USA states paired with Pd introduction and invasion timing [1] . This dataset was previously used to quantify morphometric trait shifts [3] and capture rate changes across space over Pd invasion time (Simonis et al . ; in review).…”

“…Rúa, Long-term exposure to an invasive fungal pathogen decreases Eptesicus fuscus body mass with increasing latitude, Ecosphere (2023), 14(2), e4426. https://doi.org/10.1002/ecs2.4426 [3] …”

Capture rates of Eptesicus fuscus increase following white‐nose syndrome across the eastern US

“…Changes to wildlife populations following disease emergence can be a result of spatiotemporal pathogen spread and heterogeneity of host responses to infection (e.g. physiological or behavioral) across varying landscapes (Becker et al., 2020 ; Hawley & Altizer, 2011 ; Kailing et al., 2023 ; Lopes et al., 2021 ; Simonis, Hartzler, Turner, et al., 2023 ). These responses can also differentiate across demographics within a population due to differences in prevalence, infection intensity, and/or survival between male and female hosts (Kailing et al., 2023 ; Retschnig et al., 2014 ; Russell et al., 2019 ).…”