Scaling‐up the biodiversity–ecosystem functioning relationship: the effect of environmental heterogeneity on transgressive overyielding

Abstract

Knowledge of how biodiversity sustains ecosystem function comes predominantly from studies focused on small spatial scales. Thus, we know relatively little about the role of biodiversity at larger scales of space and time where habitats become increasingly heterogeneous. Efforts to upscale the relationship between biodiversity and function have yielded inconclusive results. Given that increasing habitat heterogeneity is a ubiquitous consequence of increasing spatial scale, we asked: as habitat heterogeneity increases, can single species continue to maintain ecosystem function? Or, does transgressive overyielding (functioning of species mixture divided by the functioning of the highest functioning single species) change with habitat heterogeneity? We addressed this using a combination of computer simulations, an experiment and a meta‐analysis. The three parts followed the same rationale: habitat heterogeneity was increased by aggregating local habitats with different conditions into larger and more heterogeneous landscapes. The computer simulations showed that, on average, transgressive overyielding increased with habitat heterogeneity because monoculture functioning decreased with habitat heterogeneity. We tested this expectation experimentally by varying the strain richness from one to five species across 10800 bacterial communities in five different habitats defined by sub‐inhibitory concentrations of antibiotics. On average, the experimental results concurred with the simulations. We tested the generality of this result using a meta‐analysis of 26 published experiments that manipulated habitat conditions and species richness. This confirmed that transgressive overyielding tended to increase with habitat heterogeneity but only when species were specialised to different habitats and were not inhibited in mixtures by negative species interactions. This was not the case in several experiments used in our meta‐analysis where one species maximised functioning across all habitats, contrary to the assumptions of many ecological models. Our results illustrate the importance of biodiversity at larger spatial scales with more heterogeneity but also highlights contingencies that this pattern depends on.

Macroalgae maintain growth outside their observed distributions: Implications for biodiversity‐ecosystem functioning at landscape scales

“…For example, (Germain et al, 2018) found that invasion growth rates of 30 annual plant species only changed with environmental variation in the presence of interspecific competition. A recent analysis of monoculture data from 26 biodiversity-ecosystem experiments showed that in at least half of them, a single species was highest functioning in monoculture in several different environmental contexts (Gamfeldt et al, 2023). The analysis by Gamfeldt et al (2023) includes experiments spanning a range of ecosystem types (terrestrial, freshwater, marine) and organisms (e.g.…”

“…A recent analysis of monoculture data from 26 biodiversity-ecosystem experiments showed that in at least half of them, a single species was highest functioning in monoculture in several different environmental contexts (Gamfeldt et al, 2023). The analysis by Gamfeldt et al (2023) includes experiments spanning a range of ecosystem types (terrestrial, freshwater, marine) and organisms (e.g. algae, plants, fungi, primary consumers).…”

Environmental heterogeneity at two spatial scales affects litter diversity–decomposition relationships

“…When local BEF mechanisms vary with environmental context, then different BEF mechanisms (Isbell et al, 2018) and patterns (Gonzalez et al, 2020) can arise at landscape scales. The third reason is to aid in predicting how the occurrence, direction, and magnitude of biodiversity mechanisms vary along biotic and abiotic environmental gradients (Gamfeldt et al, 2023).…”

“…Species diversity can have substantial impacts on ecological processes such as primary productivity, litter decomposition, and nutrient transformation, as shown by syntheses of experimental results (Boyero et al, 2021; O'Connor et al, 2017; Srivastava et al, 2009). However, these experiments are generally performed at small spatial scales and/or under controlled environmental conditions (Cardinale et al, 2007; Gamfeldt et al, 2023). It is not clear yet how the environmental heterogeneity that characterizes larger spatial scales may affect the relationship between biodiversity and ecosystem function (BEF) (Gonzalez et al, 2020, but see Gamfeldt et al, 2023).…”

Compensation alters estimates of the number of species required to maintain ecosystem functioning across an emersion gradient: A case study with intertidal macroalgae

“…Large spatial scales are typically associated with high levels of environmental heterogeneity (Hart et al., 2017). If species respond to that environmental heterogeneity and dominate in different environmental conditions, more species may be required to maintain the rate of any given ecosystem function at large spatial scales (Gamfeldt et al., 2023; Isbell et al., 2018; Loreau et al., 2003).…”