Phylogeny reveals competition within communities and cryptic filtering by soil moisture and pH in semiarid montane plant communities, undetected by abundance-based approaches

Background Understanding plant community assembly in montane ecosystems is vital, yet mechanisms in semiarid regions remain poorly resolved, particularly regarding cryptic environmental filters.Aims We aimed to (1) determine whether lack of environment – abundance correlation reflects stochasticity or competition, and (2) evaluate whether phylogenetic structure is a more sensitive indicator of cryptic filters in semiarid mountains.Methods In 25 plots, we recorded species abundance and calculated phylogenetic metrics (NRI, NTI) from regional phylogeny. Mantel tests compared abundance – phylogeny correlations. Canonical Correspondence Analysis (CCA), PERMANOVA, and NMDS linked environmental variables (soil moisture, pH, EC; elevation, slope) to abundance. PERMANOVA and Principal Coordinates of Phylogenetic Structure (PCPS) assessed environment – phylogeny relationships.Results Abundance showed no significant correlation with environmental variables (CCA/PERMANOVA/NMDS). Mantel tests confirmed no abundance – phylogeny correlation. Phylogenetic overdispersion (negative NRI/NTI) indicated competitive exclusion. Phylogeny revealed significant filtering by soil moisture and pH (PERMANOVA) and moisture/pH/EC (PCPS) – undetected by abundance methods. Topography showed no effect.Conclusion Phylogeny revealed dual assembly dynamics: competitive overdispersion and cryptic filtering by soil moisture/pH. This shows the greater sensitivity of phylogeny, detecting deterministic filters where abundance data showed only weak trends. In semiarid mountains, local edaphic gradients override topography impact, underscoring essential role of phylogeny in revealing assembly mechanisms.