Diversity peaks at intermediate productivity in a laboratory microcosm

Area of Science:

• Ecology
• Microbial Ecology
• Evolutionary Biology

Background:

• Species diversity and ecosystem productivity are often linked, but the nature of this relationship (monotonic or unimodal) varies across natural communities.
• The underlying mechanisms driving these diverse diversity-productivity patterns remain largely unexplained, despite numerous proposed hypotheses.

Purpose of the Study:

• To propose and experimentally test a simple mechanism involving selection in heterogeneous environments to explain observed diversity-productivity patterns.
• To investigate the role of environmental heterogeneity in shaping the relationship between species diversity and productivity.

Main Methods:

• Laboratory cultures of the bacterium Pseudomonas fluorescens were used to test the proposed mechanism.
• Diverse bacterial cultures were grown across a range of nutrient concentrations to simulate varying productivity levels.
• The study compared diversity-productivity relationships in both heterogeneous and homogeneous environments.

Main Results:

• A strongly unimodal relationship between species diversity and productivity was observed in heterogeneous environments.
• In contrast, homogeneous environments did not exhibit a significant unimodal diversity-productivity relationship.
• The findings suggest that selection for specialized types in heterogeneous environments can generate the observed unimodal pattern.

Conclusions:

• Environmental heterogeneity, through selection for specialized types, can explain the unimodal diversity-productivity relationship frequently observed in natural ecosystems.
• This study provides experimental evidence supporting a key mechanism driving ecological diversity patterns.
• The results highlight the importance of environmental context in shaping the interplay between productivity and biodiversity.