Food-web constraints on biodiversity–ecosystem functioning relationships

Abstract

The consequences of biodiversity loss for ecosystem functioning and ecosystem services have aroused considerable interest during the past decade. Recent work has focused mainly on the impact of species diversity within single trophic levels, both experimentally and theoretically. Experiments have usually showed increased plant biomass and productivity with increasing plant diversity. Changes in biodiversity, however, may affect ecosystem processes through trophic interactions among species as well. An important current challenge is to understand how these trophic interactions affect the relationship between biodiversity and ecosystem functioning. Here we present a mechanistic model of an ecosystem with multiple trophic levels in which plants compete for a limiting soil nutrient. In contrast to previous studies that focused on single trophic levels, we show that plant biomass does not always increase with plant diversity and that changes in biodiversity can lead to complex if predictable changes in ecosystem processes. Our analysis demonstrates that food-web structure can profoundly influence ecosystem properties.

Diversity of protists and bacteria determines predation performance and stability

“…Here, we provide contrary evidence that diverse protists mixtures substantially reduced bacterial cell numbers ( Supplementary Figure 2). This is further supported by theory (Thebault andLoreau, 2003, 2006), suggesting that increasing generalist predator richness may have a greater effect on prey abundance than increasing specialist predator richness, as well as by field and laboratory studies (Gamfeldt et al, 2005;Byrnes et al, 2006;Griffin et al, 2008) showing that higher consumer or predator biomass because of increasing richness concomitantly resulted in reduced prey biomass.…”

Interaction intimacy organizes networks of antagonistic interactions in different ways

“…The ways in which species interactions are organized within biological systems affect different aspects of ecological and evolutionary dynamics, from community stability [1,2] to ecosystem functioning [3] and coevolution [4]. Ecologists have made substantial efforts to describe the structure and understand the assembly of ecological communities.…”

Non-omnivorous generality promotes population stability

“…In an analysis of omnivory in large complex food webs, Williams & Martinez (2004) found most species were restricted to consumption of adjacent rather than disparate trophic levels. This type of structure results in linearized food webs that appear to be more likely to experience trophic cascades (Pace et al 1999;Schmitz et al 2000;Thibault & Loreau 2003) and have higher interaction strengths that can destabilize population dynamics (McCann et al 1998). However, the number of species within trophic levels increases much faster than the number of trophic levels as species are added to a community (Williams & Martinez 2004).…”