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Experimental Evidence that Stochasticity Contributes to Bacterial Composition and Functioning in a Decomposer
Michaeline B N Albright1, Alexander B Chase1, Jennifer B H Martiny2
1Dept. of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, California, USA.
Mbio
|April 18, 2019
Summary
Stochasticity plays a role in bacterial community composition, but residual variation is a larger factor. Stochastic effects on ecosystem functions may be underestimated.
Area of Science:
- Microbial Ecology
- Community Ecology
- Ecosystem Science
Background:
- Stochasticity, arising from random events in ecological processes, is hypothesized to influence community composition.
- Quantifying stochasticity is challenging as it's often inferred from unexplained variation in beta-diversity.
- Understanding stochasticity's role is crucial for predicting biodiversity-ecosystem functioning relationships.
Purpose of the Study:
- To experimentally disentangle the roles of stochastic processes, environmental selection, and dispersal in a natural bacterial decomposer community.
- To directly measure stochastic effects on community composition and ecosystem functioning in a field setting.
- To assess the contribution of ecological drift versus residual variation to microbial community dynamics.
Main Methods:
- A field experiment using replicate nylon litterbags with controlled precipitation and dispersal treatments (open vs. closed mesh).
- Reduced initial heterogeneity to enhance detection of stochastic effects.
- Assayed microbial community composition and functional potential (enzyme activity) after 5 months.
Main Results:
- Stochasticity, particularly ecological drift, contributes to bacterial community beta-diversity.
- Residual variation accounted for significantly more variability (over four times) than previously attributed to stochasticity.
- Stochastic effects on beta-diversity were consistent at the functional level (genetic potential and enzyme activity).
- Dispersal interacted with precipitation to modulate stochasticity's contribution to functional variation.
Conclusions:
- Direct quantification of stochastic processes is essential for understanding microbial diversity and ecosystem functioning.
- While stochastic effects on taxonomic composition may be smaller than anticipated, their impact on ecosystem processes could be substantial.
- Residual variation needs careful consideration when estimating stochasticity in ecological studies.
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