Hubbell's Unified Neutral Theory of Biodiversity

Zero-sum ecological drift — species abundance distributions & rank-abundance curves

J (community size)500

θ (biodiversity θ=2Jν)20

m (immigration)0.100

θ=20, J=500: neutral theory predicts log-series SAD. Fundamental biodiversity number θ = 2Jν (ν = speciation rate). BCI forest: θ≈47.2.