Contrasting Patterns of Phyllosphere Fungal Diversity Between Angiosperms and Gymnosperms Along a Subalpine-Elevation Gradient

Abstract

Leaf functional traits play a fundamental role in shaping phyllosphere microbial diversity; however, their influence across evolutionary lineages and elevational gradients remains insufficiently understood. This study investigates the α-diversity, β-diversity, community assembly processes, and co-occurrence networks of phyllosphere fungi in Angiosperms and Gymnosperms along an elevational gradient (2900–4100 m) on Bai Ma Snow Mountain, southwestern China. By analyzing leaf functional traits and environmental factors, we evaluated their effects on fungal diversity, community assembly, and network stability under varying environmental conditions. Fungal α-diversity in Angiosperms followed a cosine-like pattern, peaking at mid-elevations, whereas Gymnosperms exhibited a consistent decline with increasing elevation. β-Diversity patterns revealed more pronounced structural shifts in Angiosperms, indicating stronger sensitivity to environmental gradients. Deterministic processes dominated community assembly at higher elevations, while stochastic processes were more influential at low-to-mid elevations, particularly in Angiosperms. Key leaf functional traits, including specific leaf area (SLA), leaf vein angle (LVA), and roughness (RS), were strongly correlated with fungal α-diversity in Angiosperms, with SLA and LVA showing negative correlations and RS a positive correlation. In contrast, Gymnosperms exhibited weaker associations with these traits. Co-occurrence network analyses revealed dynamic shifts in microbial connectivity in Angiosperms, where positive and negative interactions initially decreased but increased again at higher elevations. In contrast, Gymnosperms exhibited a steady decline in positive and negative interaction ratios along the gradient. These findings provide a foundation for integrating plant functional traits and microbial interactions into conservation strategies, prioritizing core fungal taxa, rare Angiosperms at higher elevations, and fragile alpine ecosystems, to enhance specific functional-taxa conservation and ecosystem resilience.

Keywords

angiosperms / elevational gradients / gymnosperms / leaf functional traits / microbial diversity / phyllosphere fungi

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