Assembling Stable Ecological Communities Chris Wilmers, Sitabhra Sinha and Markus Brede

Outline

Motivation

PowerPoint Presentation

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Definitions

Measures of Stability

Measures of Stability cont.

The Empiricist's View: Biodiversity is essential for maintaining community stability

Experimental evidence: Common garden experiments (e.g. Cedar Creek)

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and more resistant

Experimental evidence: Bottle Experiments (e.g. Ecotron)

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The Theoretician's View Increasing complexity leads to instability consider a simple community of one predator and one prey.

Robert May (1972) - analyzed the properties of randomly generated community matrices of,

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The Model

Model cont.

initial growth is monotonic

Community growth and collapse is more correlated than a random walk.

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stability probability density of our model vs. what we would have expected if the system had only one-step memory.

Frequency histograms for communities with different average interaction strength

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Comparison to May (1972)

Larger communities are less variable

Extinction cascades: Ratio of large to small cascades increases for decreasing community size

Larger communities are more resilient

Root mean square fluctuations

Comparing food webs to community networks

New rule: if ï¬ > 0, then eliminate the species corresponding to the most negative component of the eigenvector corresponding to the largest eigenvalue of the Jacobian A.

new rule

Provisional results:

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Acknowledgements

Author: Sitabhra Sinha

E-mail: sitabhra@imsc.res.in

Homepage: http://www.imsc.res.in/~sitabhra/

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