Estimating parameters of neutral communities: From one single large to several small samples

• Published in: Ecology (Durham) Vol. 88; no. 10; pp. 2482 - 2488
• Main Authors: Munoz, F, Couteron, P, Ramesh, B.R, Etienne, R.S
• Format: Journal Article
• Language: English
• Published: United States 01.10.2007
• Subjects: Algorithms; Animals; Biodiversity; community ecology; ecologic models; Ecology - methods; Ecosystem; estimation; field experimentation; forest ecology; Likelihood Functions; Models, Biological; plant communities; Population Dynamics; species diversity; Species Specificity; Trees - growth & development; tropical forests; India
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/07-0049.1

The neutral theory of S. P. Hubbell postulates a two-scale hierarchical framework consisting of a metacommunity following the speciation-drift equilibrium characterized by the "biodiversity number" theta, and local communities following the migration-drift equilibrium characterized by the "migration rate" m (or the "fundamental dispersal number" I). While Etienne's sampling formula allows simultaneous estimation of theta and m from a single sample of a local community, its applicability to a network of (rather small) samples is questionable. We define here an alternative two-stage approach estimating theta from an adequate subset of the individuals sampled in the field (using Ewens' sampling formula) and m from community samples (using Etienne's sampling formula). We compare its results with the simultaneous estimation of theta and m (one-stage estimation), for simulated neutral samples and for 50 1-ha plots of evergreen forest in South India. The one-stage approach exhibits problems of bias and of poor differentiability between high-theta, low-m and low-theta, high-m solution domains. Conversely, the two-stage approach yielded reasonable estimates and is to be preferred when several small, scattered plots are available instead of a single large one.