A global synthesis and meta‐analysis of the environmental heterogeneity effects on the freshwater biodiversity

Abstract

The spatial environmental heterogeneity (EH) has been invoked as an important factor to explain biodiversity. It is expected that higher spatial EH provides a wider range of resources and conditions for species with different requirements, leading to an increase of biodiversity. However, differences among geographical locations, ecosystem types, taxonomic groups, their occurrence zone, and methodological approaches may reveal idiosyncrasy between studies. Thus, we aimed to synthesize the global knowledge about the relationship between spatial EH and freshwater biodiversity (i.e. taxonomic and functional diversity, and their respective α and β components). Through a systematic review, we integrated results from 98 studies, published in 33 different countries, about the role of spatial EH – biodiversity relationship in freshwater ecosystems. Through meta‐analysis, we demonstrated that spatial EH has a positive effect over taxonomic and functional alpha diversity. Besides, we confirmed that the positive effect of spatial EH over taxonomic alpha diversity is consistent across geographical locations, ecosystem types, taxonomic groups, occurrence zones and between experiments with different methodological designs. Nonetheless, there was not enough evidence to robustly estimate the overall effect of spatial EH over taxonomic and functional beta diversity. Further, we discuss the mechanisms addressed to explain spatial EH‐biodiversity relationship, and implications for the management, conservation and restoration plans for freshwater ecosystems.