IP Fall 2006 – Neutral TheoryThe neutral theory ofbiodiversity and biogeographyIntrodution to Nee 200511 th October 2006

Background» Patterns of relative species abundances1: Tropical Wet forest2: Tropical Dry forest3: Marine Copepod4: Breeding Birds of Britain5: Tropical Bat community

Background» Which distribution?A : M acA rth ur’s Broken -Stick modelB: Log-SeriesC: Log-Normal» Log-Normal: A good but not perfectcandidate

A simple model of ecological drift» Caswell 1976> A local community of non-interacting species> The abundance of each species changesindependently from the others> New species enter rarely in the communityPr{N i – 1 | N i } = μ N iPr{N i | N i } = 1 – (λ + μ ) N iPr{N i + 1 | N i } = λ N i> Problem: the size of the community growswithout bound

Local ecological drift» Model community with J individuals» Each individual occupies one space» Each individual has an equal probability todie and it is replaced by a new individualfrom a species drawn randomly from thecommunityPr{N i –1|N i } = μ N i /J (J–N i )/(J–1) = Pr{N i +1|N i }t it i+1

Metacommunity dynamicsSpeciationMigration

The Neutral Theory of Biodiversity» The relative abundance of each species inthe metacommunity at equilibrium is afunction of:> Sample size> The fundamental biodiversity number θ» θ is the product of:> θ = 2 N u> The size of the metacommunity> The rate of speciation

Theoretical dominance-diversity curve

Theoretical dominance-diversity curves

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