Elevation shapes biodiversity patterns through metacommunity-structuring processes

Abstract

Stochastic (e.g., via species dispersal and ecological drift) and deterministic (e.g., via environmental and biotic filtering) processes can produce diversity patterns related to changes in elevation. However, existing studies have not generally examined these processes within a compressive framework. Stream macroinvertebrates are an important and diverse component of freshwater environments in high-mountain systems. By considering metacommunity-structuring processes using Hierarchical Modelling of Species Communities (HMSC), we investigated changes in taxon richness of stream macroinvertebrates along elevational gradients in streams of the Cangshan mountain range in Southwest China. We found that increasing taxon richness along the elevation gradient until the optimum was reached could be modeled using the integrated actions of full structuring processes within the metacommunity modeling. Consistent increases in taxon-richness along the elevation gradient were able to be modeled considering environmental filtering alone. In addition, the importance of structuring processes on shaping communities decreased along spatial hierarchical-scales (from local habitat to mountain-aspect levels). These results suggest that stochastic and biotic-filtering processes can confound environmental filtering in shaping macroinvertebrate communities in high-mountain streams. A comprehensive understanding of the mechanisms underlying elevational biodiversity patterns of riverine communities can be improved through quantitative frameworks (e.g., HMSC) linking metacommunity theory to the real-world systems.