Consumer versus resource control of species diversity and ecosystem functioning

Area of Science:

• Ecology
• Marine Biology
• Ecosystem Dynamics

Background:

• Ecological research traditionally focused on either resource supply (productivity) or consumers/disturbance as primary drivers of species diversity.
• Previous studies often showed unimodal relationships between these factors and diversity when studied in isolation.
• Multivariate models predict complex interactions between productivity, consumers, and disturbance influencing community diversity.

Purpose of the Study:

• To test the predictions of multivariate models regarding the interactive effects of nutrient supply and consumer pressure on species diversity.
• To investigate how these interactions vary across marine food webs with differing productivity levels.
• To determine if observed patterns extend to ecosystem functions like carbon storage and nitrogen retention.

Main Methods:

• Field manipulations of nutrient resources and consumer pressure were conducted on rocky shores with contrasting productivity.
• A factorial meta-analysis of published experiments was used to confirm findings across diverse aquatic communities.
• Measurements of species diversity and ecosystem functions (carbon storage, nitrogen retention) were performed.

Main Results:

• The effects of consumers and nutrients on species diversity were consistently interdependent.
• The direction of these effects and the point of peak diversity shifted between low and high productivity sites.
• These interactive patterns were confirmed across various aquatic ecosystems through meta-analysis.

Conclusions:

• Species diversity and ecosystem functioning are jointly regulated by the interplay of nutrient supply and food-web structure.
• Human impacts on nutrient levels and food webs have significant, interconnected consequences for biodiversity and ecosystem services.
• Effective management strategies must address nutrient supply and food-web dynamics concurrently.