Entomopathogenic Metarhizium and Beauveria species are associated with distinct geographic, management, and environmental factors, as well as plant communities

Entomopathogenic fungi of the genera Metarhizium and Beauveria are important natural regulators of arthropod populations. To investigate their distribution and ecological drivers in real-world permanent grasslands, we did a survey analyzing fungal communities across 72 sites in Switzerland using ITS2 amplicon sequencing. We identified 10 Metarhizium and six Beauveria amplicon sequence variants (ASVs), with at least one ASV present at every site. Frequent ASVs included M. robertsii / M. pingshaense , M. brunneum , B. bassiana , and B. brongniartii . These ASVs showed distinct presence/absence and abundance patterns, indicating adaptation to climatic, soil physicochemical, and management-related factors. Factors such as soil pH, available phosphorus, temperature, bulk soil density, and management intensity significantly correlated with ASV distributions. For example, M. robertsii / M. pingshaense was widely distributed but strongly associated with soil pH, while B. brongniartii was restricted to subalpine regions, correlating with lower temperatures and nutrient levels. Plant communities, plant community-derived ecological indicator values (EIVs) reflecting environmental conditions, and indicator plant species analysis showed correlations with specific ASVs. On one hand, this suggests shared ecological niches and/or indicates possible direct plant–fungal interactions, consistent with the known endophytic or root-associated lifestyles of some entomopathogenic fungi. On the other hand, it suggests that plant-derived EIVs and individual indicator plant species may serve as effective indices for identifying habitats suitable for the presence and establishment of these entomopathogenic fungi. This approach may facilitate the evaluation of the suitability of particular environments for the application of Metarhizium and Beauveria strains as biological control agents. IMPORTANCE The globally occurring fungal entomopathogens Metarhizium and Beauveria are key natural regulators of soil-dwelling arthropods and are widely used as biological control agents. Yet predicting their presence or potential to establish in particular habitats and provide their ecosystem function remains challenging. This survey study in real-world grasslands reveals distinct ecological niches characterized by climatic, soil physicochemical, and management parameters for different Metarhizium and Beauveria taxa. In addition, we demonstrate that plant community composition, plant-derived ecological indicator values, and individual indicator plant species are associated with Metarhizium and Beauveria presence and abundance. Our findings suggest that, within this regional context, vegetation data may serve as praxis-oriented proxies for efficient and non-invasive assessment of site suitability both for native fungal populations and biological control agents of selected Metarhizium and Beauveria taxa in grassland ecosystems.