Global Soil Fauna Metacommunity Patterns: The Roles of Spatial Extent and Environmental Heterogeneity

A central debate in metacommunity theory concerns how the relative importance of ecological processes varies with spatial scale. We addressed this by integrating global soil fauna metacommunity datasets to analyze the effects of spatial extent (the specific dimension of scale examined) and environmental factors on metacommunity patterns using Bayesian models. Results suggested that increasing spatial extent was strongly associated with a higher prevalence of Clementsian patterns. Notably, this relationship was not explained by the concomitant environmental variables, which may be consistent with the influence of latent spatial properties (e.g., dispersal limitation) or unobserved environmental heterogeneity at broader scales. Conversely, environmental factors independently were associated with other patterns. Notably, the effect of soil nitrogen on checkerboard patterns was context-dependent: it suppressed species segregation under low spatial turnover (βSIM) but potentially weakened or shifted to facilitation under high turnover. This suggests that resource enrichment alters the balance between niche-based and neutral processes. Although further verification in under-sampled climatic zones is required, our synthesis supports a hierarchical driver framework: spatial extent emerges as a key correlation of broad distributional order, whereas resource availability is suggested to regulate the prevalence of competitive exclusion at finer resolutions.