Reconciling neutral community models and environmental filtering: theory and an empirical test

Authors

  • Franck Jabot,

  • Rampal S. Etienne,

  • Jérôme Chave


F. Jabot and J. Chave (chave@cict.fr), Laboratoire Evolution et Diversité Biologique CNRS, Univ. Paul Sabatier Bâtiment 4R3, FR–31062 Toulouse cedex 4, France. FJ also at: AgroParisTech-Ecole Nationale du Génie Rural, des Eaux et des Forêts, 19 avenue du Maine, FR–75015 Paris, France. – R. S. Etienne, Community and Conservation Ecology Group, Univ. of Groningen, PO Box 14, NL–9750 AA Haren, the Netherlands.

Abstract

It is widely believed that the neutral theory of biodiversity cannot be used for parameter inference if the assumption of neutrality is not met. The goal of this work is to extend this neutral framework to quantify the intensity of recruitment limitation (limited dispersal plus environmental filtering) in natural species assemblages. We model several local communities as part of a larger metacommunity, and we assume that neutrality holds in each local community, but not in the metacommunity. The immigration rate m does not only reflect dispersal limitation into a given local community, but also the intensity of environmental filtering. We develop a novel statistical method to infer the immigration parameter m in each local community. Using simulated datasets, we show that m indeed depends on both dispersal limitation and on the intensity of environmental filtering. We then apply this method to a network of tropical tree plots in central Panama. Inferred recruitment rates m were positively correlated with the fraction of trees dispersed by mammals, and with annual rainfall, possibly due to a weaker environmental filtering as rainfall increases. Finally, m, as estimated from trees greater than 1 cm trunk diameter, were significantly larger than an estimation based on trees greater than 10 cm trunk diameter. This suggests a cumulative effect of environmental filtering upon trees throughout their ontogeny.

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