Dispersal scales up the biodiversity–productivity relationship in an experimental source-sink metacommunity

Abstract

The influence of biodiversity on ecosystem functioning is a major concern of ecological research. However, the biodiversity -ecosystem functioning relationship has very often been studied independently from the mechanisms allowing coexistence. By considering the effects of dispersal and niche partitioning on diversity, the metacommunity perspective predicts a spatial scale-dependence of the shape of the relationship. Here, we present experimental evidence of such scale-dependent patterns. After approximately 500 generations of diversification in a spatially heterogeneous environment, we measured functional diversity (FD) and productivity at both local and regional scales in experimental source-sink metacommunities of the bacterium Pseudomonas fluorescens SBW25. At the regional scale, environmental heterogeneity yielded high levels of FD and we observed a positive correlation between diversity and productivity. At the local scale, intermediate dispersal increased local FD through a mass effect but there was no correlation between diversity and productivity. These experimental results underline the importance of considering the mechanisms maintaining biodiversity and the appropriate spatial scales in understanding its relationship with ecosystem functioning.

Competition–colonization dynamics in experimental bacterial metacommunities

“…As opposed to other regional mechanisms of species coexistence that have found a positive biodiversity-ecosystem function (BEF; for example, source-sink dynamics 30,31 ), our experiment showed how CC dynamics may produce a rarely observed negative BEF relationship 32,33 , which is likely explained by a combination of patch dynamics and the regional dominance of a productive and competitive species (a 'negative selection effect', sensu 34 ). These results suggest that the definition of complementarity and selection effects, as the main drivers underlying the BEF relationship, may need to be revisited to accommodate broader coexistence mechanisms.…”

“…A prime example of the potential applications of our framework is the demonstration that the effects on landscape-level coexistence could be closely linked to those on regional level BEF relationships, suggesting that the effects of fragmentation on extinction debts may also cascade to ecosystem attributes. Our findings illustrate that BEF relationships may depend on the spatial scale over which they occur and the mechanisms generating the gradient of diversity 29,30,38 .…”

Positive Effects of Bacterial Diversity on Ecosystem Functioning Driven by Complementarity Effects in a Bioremediation Context

“…The importance of bacteria for the functioning of ecosystems is well known [7], [8] but the impact of bacterial diversity on ecosystem functions is highly variable depending on the environmental conditions, with experimental evidence suggesting either positive [9]–[15], neutral [10], [16] or negative [15], [17] effects on functioning. Additionally, while both the number and identity of species has been suggested to be important for the functioning of bacterial communities [9]–[12] little is known about the underlying mechanisms.…”

Bacterial farming by the fungusMorchella crassipes

“…At a microscopic scale, discrete water films restrict the dispersal of individual microbial cells or populations [17]. The link between diversity and dispersal [18,19] has led to the hypothesis that bacterial diversity in soils partly reflects the limitation to free dispersal in water-unsaturated media [20,21].…”