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THE UNIFIED NEUTRAL THEORY OF BIODIVERSITY AND BIOGEOGRAPHY: COMMENT
Author(s) -
Chisholm Ryan A.,
Burgman Mark A.
Publication year - 2004
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/04-0228
Subject(s) - biodiversity , biogeography , ecology , geography , biology
The Unified Neutral Theory of Biodiversity and Biogeography (Hubbell 2001) is a formal mathematical theory that seeks to explain observed patterns of relative species abundance (RSA) and species richness in ecological communities. Simulations of the theory's dynamics have to date suggested that at equilibrium the local community RSA distribution has a particular lognormal-like shape, one that is commonly observed in natural communities (Hubbell 2001). Here we show that under low immigration rates the true equilibrium distribution predicted by the Unified Theory has a distinctly different shape to that proposed previously. The Unified Theory is developed by incorporating a speciation rate into the classical theory of island biogeography (MacArthur and Wilson 1967). Under the key assumption of neutrality, all individuals of all species in a trophically defined community are ecologically equivalent on a per capita basis (Hubbell 2001). The Unified Theory predicts the existence of a dimensionless "fundamental biodiversity number," 0, equal to 2Jv, where JM is the number of individuals in the metacommunity and v is the speciation rate (Hubbell 2001). The species richness and RSA in the metacommunity are then predicted solely by 0 and JM. Hubbell showed that for a nonoverlapping generations model, the RSA distribution in the metacommunity approaches Fisher's logarithmic series (log-series) distribution (Fisher et al. 1943) as J, c, although it is not identical to it.