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
Reviews of Neutral Models
Levine & HilleRisLambers (2009) Nature 461:254.
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
Bell, Lechowitz &Waterway (2006) Ecology 87:1378.
Niches vs immigration
Predicted static patterns similar
Experimental results strongly favor niche theory
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.”
Purves & Turnbull (2010) J Animal Ecology 79:1215.
Stress implausibility of growth-rate equality assumed by NCM
Neutrality highly implausible
Gotelli & McGill (2006) Ecography 29:793
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.
Levine & HilleRisLambers (2009) Nature461:254.
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
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
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
Species Not Equivalent
2 Orders of Magnitude in Geometric Mean
Neutral Model Assumptions:
Self-Regulation Equal to Between-Species Effect
Control (Niche differences)
H’ 50% Greater
Rare Species 35% Community
Rare Species 8% Community
Common Species More Common
Signature of Coexistence via Self-Regulation