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Niches versus Neutrality Reviews of Neutral Models Levine & HilleRisLambers (2009) Nature 461:254.

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Presentation on theme: "Niches versus Neutrality Reviews of Neutral Models Levine & HilleRisLambers (2009) Nature 461:254."— Presentation transcript:

1 Niches versus Neutrality Reviews of Neutral Models Levine & HilleRisLambers (2009) Nature 461:254.

2 Reviews Hubbel (2001) The Unified Neutral Theory of Biodiversity and Biogeography. Princeton University Press. Zero Sum Multinomial for Species Abundances Tuning Parameters, NCM versions of niche-preemption to lognormal species abundances

3 Reviews Bell, Lechowitz &Waterway (2006) Ecology 87:1378. Niches vs immigration Predicted static patterns similar Experimental results strongly favor niche theory

4 Reviews McGill, Maure & Weiser (2006) Ecology 87:1411. Review testing neutral theory statistically Available tests fail to support neutrality (only 1 exception) Develop new test to distinguish zero-sum multinomial from lognormal species abundances Neutral theory: Estimating parameters difficult/arbitrary “… overwhelming evidence against neutral theory.”

5 Reviews Purves & Turnbull (2010) J Animal Ecology 79:1215. Stress implausibility of growth-rate equality assumed by NCM Neutrality highly implausible Similar views: Gotelli & McGill (2006) Ecography 29:793

6 Niches and Neutrality Currently, neutral models (approx. 10) lack both conceptual strength and empirical support. Neutral models remind us that ecology, as a science, should link pattern (at a given scale) to process (often at a more restricted scale); description and statistical fit model prediction do not validate model.

7 Niches and Maintenance of Diversity Levine & HilleRisLambers (2009) Nature 461:254.

8 Levine & HilleRisLambers (2009) Maintenance of ecological diversity Functional, economic & aesthetic Coexistence: Competitors’ niches differ; Stabilizes density-dependent dynamics, Per-capitum growth greater when rare Challenge: Neutral theory: here, density-independent growth rates

9 Levine & HilleRisLambers (2009) Left: Self-Regulation Stronger than Interspecific Effect Higher Growth Rate When Rare Produces Coexistence Right: No Niche Difference, Implying Within-Species and Between-Species Effects Same

10 Levine & HilleRisLambers (2009) Annuals on Serpentine Soils Sites: 10+ Species Co-Occur Diversity Niche Based? Planted Experimental Communities Each 10 Species Equal Relative Abundances Growth-Rate Differences Reflect Inherent Differences, Density-Variation Controlled

11 Levine & HilleRisLambers (2009) Species Not Equivalent 2 Orders of Magnitude in Geometric Mean Neutral Model Assumptions: Self-Regulation Equal to Between-Species Effect Discrete-Time Dynamics: Competitive Exclusion

12 Species Diversity Seed pools control (any niche effects) Niches removed (equal effects) Control (Niche differences) H’ 50% Greater Rare Species 35% Community Niches Removed Rare Species 8% Community Common Species More Common

13 Self-Regulated Growth: Seed Production Signature of Coexistence via Self-Regulation Niche Differences


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