Anthropogenic impact on soil fungi of tropical dry forest

Introduction: Tropical dry forest ecotones rely on soil fungal communities for nutrient cycling and ecosystem stability. The Sathyamangalam Tiger Reserve (STR) in Tamil Nadu, India, acts as a crucial biogeographical bridge between the Eastern and Western Ghats. This study evaluated structural and functional shifts in soil mycobiomes exposed to physical human encroachment within this protected ecotone. Materials and methods: Environmental DNA (eDNA) metabarcoding of the fungal internal transcribed spacer (ITS) region was performed using Illumina NextSeq 550 sequencing. Two composite soil libraries ( n = 1 per zone, each pooled from nine sub-cores) were analyzed from the Hasanur division: a conserved forest zone (CFZ) and an anthropogenically impacted zone (AIZ). QIIME 2 and DADA2 processed sequences against the UNITE database, with functional roles inferred via FUNGuild. Results: High-throughput processing generated 149,703 high-quality reads, resolving into 247 species-level amplicon sequence variants (ASVs). Observed species richness dropped sharply in the AIZ (60 species, 55 families) compared to the CFZ (223 species, 116 families). While Ascomycota and Basidiomycota dominated both regimes (>79% relative sequence abundance), lower-abundance phyla showed marked compositional shifts. The AIZ exhibited increased relative sequence representation of Mortierellales and arbuscular mycorrhizal fungi (Glomerales), alongside reduced Chytridiomycota (4.13% in the CFZ compared to 0.28% in the AIZ). Functional profiling indicated decreased relative sequence abundance of specialized lignicolous saprotrophs ( Ganoderma eickeri , Polyporus sp.) and microclimate-associated yeasts ( Hannaella sp., Vishniacozyma sp.) in the AIZ. Additionally, 18 species-level candidate taxa unlisted in regional checklists were detected, providing targets for future multi-locus validation. Conclusions: Soil fungal communities exhibited marked structural and compositional differences between management regimes, with the impacted perimeter displaying a restricted species pool dominated by generalist and ruderal lineages compared to the intact forest core. These descriptive snapshots highlight the importance of conserving undisturbed dry forest tracts to maintain specialized soil fungal diversity across tropical ecotones.