Estimating parameters of neutral communities: from one single large to several small samples
2007
Munoz, François | Couteron, Pierre | Ramesh, B. R. | Etienne, R. S.
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” ?, 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 ? 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 ? 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 ? 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-?, low-m and low-?, 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.
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