Abstract
Understanding how species-rich communities persist is a foundational question in ecology. In tropical forests, tree diversity is structured by edaphic factors, climate, and biotic interactions, with seasonality playing an essential role at landscape scales: wetter and less seasonal forests typically harbor higher tree diversity than more seasonal forests. We posited that the abiotic factors shaping tree diversity extend to hyperdiverse symbionts in leaves—fungal endophytes—that influence plant health, function, and resilience to stress. Through surveys in forests across Panama that considered climate, seasonality, and covarying biotic factors, we demonstrate that endophyte richness varies negatively with temperature seasonality. Endophyte community structure and taxonomic composition reflect both temperature seasonality and climate (mean annual temperature and precipitation). Overall our findings highlight the vital role of climate-related factors in shaping the hyperdiversity of these important and little-known symbionts of the trees that, in turn, form the foundations of tropical forest biodiversity.
Highlights
Understanding how species-rich communities persist is a foundational question in ecology
We rarefied and log-transformed endophyte species richness for each plant (37 plant collections representing 26 species, 24 genera, 20 families, and 14 representative orders of angiosperms; Supplementary Data 2), verified that sampling was sufficient for intersite comparisons (Supplementary Fig. 1), and compared richness between the drier, more seasonal forest and the wetter, less seasonal forest, taking into account leaf defenses, which were predicted to differ between forests based on previous studies[3]
The highly diverse plant communities in tropical forests support diverse assemblages of associated organisms whose distributions may be predicted to track those of the plants with which they affiliate
Summary
Understanding how species-rich communities persist is a foundational question in ecology. Endophytes may demonstrate structure across tropical forests that can be traced directly to climate-related factors, consistent with the regional endemism and local uniqueness of plant communities that are defined by marked climate gradients in tropical regions[2,3,9] and in line with the potential for local, functional specialization of endophyte assemblages under particular biotic or abiotic regimes[7,27] Evaluating these predictions requires landscape-scale surveys that take into account climate and seasonality, and the many biotic factors that shift with these major drivers of biodiversity, including climate- and seasonality-related gradients of plant community composition, richness, and phylogenetic diversity; plant functional traits, such as chemical and physical defenses; and vegetation structure, which can influence the heterogeneity and suitability of local environments for fungal life cycles Understanding the affiliations of endophytes for particular climate regimes is key to charting their diversity and roles in ecosystem services at a regional and global scale
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