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Dryad

Data from: Increasing prevalence of plant-fungal symbiosis across two centuries of environmental change

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Nov 05, 2024 version files 853.69 KB

Abstract

Species' distributions and abundances are shifting in response to ongoing global climate change.  Mutualistic microbial symbionts can provide their hosts with protection from environmental stress that may contribute towards resilient responses to environmental change, however these changes may also disrupt species interactions and lead to declines in hosts and/or symbionts. Symbionts preserved within natural history specimens offer a unique opportunity to quantify changes in microbial symbiosis across broad temporal and spatial scales.  We asked how the prevalence of seed-transmitted fungal symbionts of grasses (Epichloë endophytes) have changed over time in response to climate change, and how these changes vary across host species' ranges. Specifically, we analyzed 2,346 herbarium specimens of three grass host species (Agrostis hyemalis, Agrostis perennans, Elymus virginicus) collected over the past two centuries (1824-2019) for the presence or absence of Epichloë symbiosis.  We found that endophytes increased in prevalence over the last two centuries from ca. 25% prevalence to ca. 75% prevalence, on average, across three host species. Changes in seasonal climate drivers were associated with increasing endophyte prevalence.  Notably, increasing precipitation during the peak growing season for Agrostis species and decreasing precipitation for E. virginicus were associated with increasing endophyte prevalence. Changes in the variability of precipitation and temperature during off-peak seasons were also important predictors of increasing endophyte prevalence. Our analysis performed favorably in an out-of-sample predictive test with contemporary survey data, a rare extra step in collections-based research. However, we identified greater local-scale variability in endophyte prevalence in contemporary data compared to model predictions based on historic data, suggesting new directions that could improve predictive accuracy. Our results provide novel evidence for a cryptic biological response to climate change that may contribute to the resilience of host-microbe symbiosis through context-dependent benefits that confer a fitness advantage to symbiotic hosts under environmental change.