Fungal Community Composition Varies Across Floral and Extrafloral Nectaries.

Floral (FNs) and extrafloral nectaries (EFNs) are key plant microhabitats that mediate interactions among plants, insects, and microorganisms, yet their associated fungal communities remain poorly characterized, especially in tropical ecosystems. Here, we investigated the diversity, taxonomic composition, and functional structure of fungal communities across distinct plant microhabitats of two woody Cerrado species, Maprounea brasiliensis and Hymenaea stigonocarpa, using an environmental DNA metabarcoding approach. In M. brasiliensis, fungal communities from floral and extrafloral nectaries were compared, whereas in H. stigonocarpa, extrafloral nectaries were contrasted with adjacent phyllosphere and endosphere compartments. Across all microhabitats, communities were dominated by Ascomycota, with Cladosporium as the most abundant genus. Yeast genera such as Hannaella, Starmerella, and Aureobasidium, although less abundant than filamentous fungi, were also consistently detected as part of the core mycobiota across both plant species and compartments. In M. brasiliensis, EFNs exhibited higher richness, diversity, and evenness than FNs, and beta diversity analyses revealed clear compositional differentiation between these nectary types. In contrast, no significant differences in alpha or beta diversity were detected between EFNs and phyllosphere/endosphere compartments of H. stigonocarpa. Functional profiles were dominated by plant pathogenic and saprotrophic fungi in all microhabitats, with filamentous forms prevailing over yeasts. However, yeast-like growth forms were relatively more abundant in the EFNs of M. brasiliensis. These results show that floral and extrafloral nectaries act as ecologically distinct microhabitats that contribute to fungal community structuring in Cerrado plants, with implications for plant-insect-microbe interactions in a highly diverse and understudied biome.