Global drivers of phyllosphere fungal diversity in sentinel plantings

Foliar fungal communities are fundamental to tree health, ecosystem functioning, and forest resilience. Understanding the ecological drivers of these communities is essential for predicting forest responses to stressors like climate change and emerging pathogens. Large-scale patterns of these drivers, however, remain poorly understood, as most studies are restricted to limited geographic regions or a few host species. In this study, a network of ex patria sentinel plantings where 32 tree species were cultivated outside their native ranges across North America, Europe, and Asia, provides a powerful platform to address this knowledge gap. Within this framework, high-throughput sequencing of the foliar mycobiome was used to evaluate the relative influence of geographic location, host identity and phylogeny, sampling season, and health status on fungal community assembly. This experimental design allows for the disentanglement of complex, often-confounded drivers, offering critical insights into the environmental filtering of local microbes onto non-native trees and the potential biosecurity risks they may pose.