Evenness effects mask richness effects on ecosystem functioning at macro-scales in lakes

Area of Science:

• Ecology
• Environmental Science

Background:

• Biodiversity-ecosystem functioning (BEF) theory traditionally emphasizes species richness.
• Emerging evidence suggests that species evenness may play a more critical role in ecosystem functioning.
• Conflicting findings exist, with small-scale studies often showing positive relationships and regional studies documenting negative impacts of evenness.

Discussion:

• This research investigates the prevalence and consistency of evenness effects on ecosystem functioning across broad spatial scales.
• The study utilizes a comprehensive lake dataset from the continental US, examining phytoplankton and zooplankton.
• It assesses whether BEF relationships vary across different regions and trophic levels.

Key Insights:

• At the continental scale, phytoplankton evenness was a stronger predictor of phytoplankton and zooplankton resource use efficiency (RUE) than species richness.
• Regional analyses consistently showed negative relationships between phytoplankton evenness and phytoplankton RUE, and positive relationships with zooplankton RUE.
• The observed patterns in evenness effects were largely consistent across diverse US regions, indicating their widespread nature.

Outlook:

• Findings suggest that negative impacts of evenness on ecosystem functioning may be more prevalent than previously recognized.
• These effects are not confined to highly disturbed ecosystems but appear common in natural lake systems.
• Further research should explore the mechanisms driving these widespread evenness effects and their implications for ecosystem management.