Ecologists have long sought to understand how changes in ecosystem productivity shape the biodiversity. Studies have shown that productivity and species richness may be positively related, negatively related, or hump-shaped, with the richness peaking at intermediate productivity.

This pattern has been confirmed mainly in plant communities. However, in animal communities, especially in complex fish assemblages, it hasn't been confirmed because of interacting ecological processes and the difficulty in obtaining quantitative data. Besides, how to explain this pattern within a unified theoretical framework remains unclear.

In a study published in Ecology Letters, an international team led by Prof. WANG Qidong from the Institute of Hydrobiology of the Chinese Academy of Sciences proposed a new unified model to reveal the unimodal relationship between productivity and species richness in fish communities.

Quantitative data from 39 shallow lakes in middle and lower reaches of the Yangtze River was collected during field surveys. Researchers confirmed a stable hump-shaped productivity-species richness relationship in fish communities: As productivity rose, diversity first increased and then declined. This finding demonstrated that biodiversity cannot increase indefinitely with greater energy input, providing a basis for understanding fish community shifts under eutrophication.

Researchers proposed a unified model which integrates three core hypotheses: the More Individuals Hypothesis, the Biomass-Driven Competition Hypothesis, and the Environmental Filter Hypothesis. This model combines observed patterns with ecological theory and statistical modeling, and reconstructs the unimodal relationship observed in lake fish communities. It provides a quantifiable, testable mechanistic explanation for the productivity-diversity issue.

Moreover, researchers found the evidence for intensified species interactions along a productivity gradient in animal communities. Competition-driven losses occurred before diversity declines caused by environmental stress (e.g., hypoxia) and offset any richness gains from higher abundance, suggesting that biodiversity decline may serve as an early warning of ecosystem degradation.

This study strengthens the understanding of structural stability in lake ecosystems. It emphasizes that management should prioritize the dynamic balance and trade-offs between productivity and diversity, rather than focusing only on fish yield or species counts.