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Niches versus Neutrality. Reviews of Neutral Models Levine & HilleRisLambers (2009) Nature 461:254. Reviews. Hubbel (2001) The Unified Neutral Theory of Biodiversity and Biogeography . Princeton University Press. Zero Sum Multinomial for Species Abundances

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Niches versus neutrality

Niches versus Neutrality

Reviews of Neutral Models

Levine & HilleRisLambers (2009) Nature 461:254.


Reviews
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


Reviews1
Reviews

Bell, Lechowitz &Waterway (2006) Ecology 87:1378.

Niches vs immigration

Predicted static patterns similar

Experimental results strongly favor niche theory


Reviews2
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.”


Reviews3
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


Niches and neutrality
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.


Niches and maintenance of diversity

Niches and Maintenance of Diversity

Levine & HilleRisLambers (2009) Nature461:254.


Levine hillerislambers 2009
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


Levine hillerislambers 20091
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


Levine hillerislambers 20092
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


Levine hillerislambers 20093
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


Species diversity seed pools control any niche effects niches removed equal effects
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


Self regulated growth seed production
Self-Regulated Growth: Seed Production

Signature of Coexistence via Self-Regulation

Niche Differences


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