Neotropical Cave Entrances as Environmental Filters for Vascular Plant Communities Along Low‐Light and Soil Resource Gradients

Aims Cave entrances are low‐light, oligotrophic ecotones where vascular plants persist at the intersection of strong constraints imposed by light, moisture, and soil resources. Yet the processes structuring these communities in tropical regions remain poorly explored. We ask: (1) How do vascular plant richness and composition change along depth‐defined zones across the forest–cave continuum? (2) Which features of external forest structure, entrance geomorphology, and soil–sediment geochemistry best explain among‐entrance β ‐diversity? (3) Within entrances, is compositional change driven primarily by species turnover or by richness loss under increasing edaphic stress? Location Neotropical quartzite cave entrances in tropical montane environments. Methods We surveyed forest structure and vascular plant communities across depth‐defined entrance zones, quantified soil and sediment geochemistry from the forest edge into the subterranean environment, and modeled richness and β ‐diversity using generalized linear mixed models, β ‐diversity partitioning and Bayesian bootstrap generalized dissimilarity modeling (BBGDM). Results Species richness declined steeply with increasing depth, although angiosperms persisted into dim‐light zones. Among entrances, β ‐diversity was high and was most strongly associated with variation in external forest structure, entrance geomorphology and geochemical gradients along the forest–cave interface. Within entrances, compositional shifts were dominated by richness loss rather than turnover, consistent with strong edaphic filtering linked to declining organic matter and increasingly quartz‐rich, aluminous sediments. Conclusions Light availability, external forest structure, and soil geochemistry jointly govern vascular plant communities at subterranean–epigean interfaces. Although our analyses do not directly test climatic buffering, the persistence of shade‐ and stress‐tolerant species in low‐light, organically enriched entrance sectors suggests that tropical cave entrances are promising systems for future studies of microrefugial function under climate change.