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Species diversity in local neutral communities.
Xin-Sheng Hu1, Fangliang He, Stephen P Hubbell
1Department of Renewable Resources, 751 General Service Building, University of Alberta, Edmonton, Alberta T6G 2H1, Canada. xin-sheng.hu@ualberta.ca
The American Naturalist
|January 4, 2008
Summary
This study enhances macroecology's neutral theory by modeling biodiversity in local-metacommunity systems. It reveals that immigration variance reduces species diversity, and local patterns mirror metacommunity diversity at larger scales.
Area of Science:
- Ecology
- Macroecology
- Biodiversity Science
Background:
- The neutral theory of macroecology provides a framework for understanding biodiversity patterns.
- Current models often treat local communities as isolated or implicitly defined within a metacommunity.
- Spatially implicit models may impose artificial distinctions between community scales.
Purpose of the Study:
- To extend the neutral theory of macroecology by developing biodiversity models for embedded local community-metacommunity systems.
- To investigate the impact of local speciation and immigration rate stochasticity on local species diversity.
- To establish a relationship between the fundamental diversity parameter and Simpson's index.
Main Methods:
- Derivation of biodiversity models, including relative species abundance and species-area relationships.
- Analysis of local species diversity patterns in relation to metacommunity size and immigration rates.
- Introduction of stochasticity into immigration rates and removal of speciation restrictions in local communities.
Main Results:
- Local species diversity patterns converge to metacommunity patterns as local community size increases, challenging the notion of sharp boundaries.
- Allowing for local speciation, even at small effects, and introducing stochasticity in immigration rates are key extensions.
- High variance in immigration rates was shown to reduce species diversity in local communities.
- A simple relationship was found between the fundamental diversity parameter of neutral theory and Simpson's index.
Conclusions:
- The spatial scale of a local community influences its diversity patterns, which tend to align with the broader metacommunity.
- Stochasticity in immigration rates, particularly high variance, acts as a significant driver of reduced local species diversity.
- The derived relationship between the fundamental diversity parameter and Simpson's index offers a new tool for assessing immigration effects on biodiversity estimates.
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