Environmental Gradients Shape Mammal and Galliform Bird Communities in a Mountain Reserve Through Species Turnover and Niche Differentiation

Protected areas are often treated as internally homogeneous conservation units, yet their communities may be structured either as discrete modules or as continuous gradients shaped by environmental heterogeneity and human disturbance. Using camera-trap data from Liziping Nature Reserve, China, we examined the spatial organization of mammal and galliform bird communities and tested whether species-level environmental responses help explain community structure. From 109 camera-trap sites surveyed between October 2017 and July 2020, we obtained 6688 independent detections and retained 17 species for analysis. We combined β-diversity decomposition, clustering, NMDS ordination, single-species occupancy models, clustering of environmental response coefficients, and Mantel tests. Community variation was dominated by turnover rather than nestedness, and clustering based on co-occurrence and relative activity patterns did not reveal well-separated discrete modules. Instead, NMDS indicated continuous variation along environmental gradients, with elevation and vegetation productivity as the strongest correlates. Occupancy models showed marked species-specific environmental responses, especially to elevation, habitat structure, and human disturbance, and β-based clustering suggested two broad environmental response groups. Although human influences did not affect all species uniformly, some species showed clear sensitivity to recent disturbance and human-modified landscapes. These results indicate that communities in Liziping are better characterized as continuous gradient structures than as discrete modules, and suggest that conservation should emphasize the maintenance of environmental heterogeneity, habitat continuity, connectivity, and differentiated management of human activities within mountain protected areas.