COS 23-5 - Variation in per capital speciation rate and diversity patterns in neutral and niche-structured communities

Tuesday, August 9, 2011: 9:20 AM
9AB, Austin Convention Center
Shaopeng Wang1, Anping Chen2, Stephen W. Pacala2 and Jingyun Fang3, (1)Centre for Biodiversity Theory and Modelling, Station d'Ecologie Expérimentale du CNRS à Moulis, France, (2)Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, (3)State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China

Speciation has long been viewed as a fundamental driver for shaping the diversity patterns of ecological communities. Hubbell’s theoretical work on the ecological “neutral theory” makes it possible to model the effect of speciation rate on species diversity and abundance distribution. However, most of previous models assume a constant per capita speciation rate across all species, which is not true for most taxa. In this study, we investigate how different possible scenarios, both interspecific asymmetric and symmetric, of variations in per capita speciation rate could impact species diversity and abundance distribution in a neutral community or a hybrid metacommunity which is divided into numerous local communities isolated through niche governed processes but dynamics within each local community is governed by neutral drifts.


We first relax the constant per capita speciation rate assumption with uniform randomness in per capita speciation rate. Numerical simulation shows that in a closed neutral community, randomness of per capita speciation rate would result in a negative relationship between per capita speciation rate and population size. Consequently this negative speciation rate – abundance relationship could bring about more abundant species compared with Hubbell’s constant per capita speciation scenario. In contrast, a positive relationship between per capita speciation rate and population size generates more rare species and less abundant species, and hence increases species richness.

These results also hold for the hybrid niche-neutral metacommunity when the number of niche is moderate. Niche partitioning can decrease or increases the mean speciation rate by reducing average population size, under positive or negative abundance dependent speciation scenarios, respectively. The effect of speciation rate on the metacommunity diversity pattern gradually diminish with increased niche partitioning, i.e., the number of isolated sub-communities.

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