Changes in Individual Allometry Can Lead to Species Coexistence without Niche Separation |
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Authors: | Edward B Rastetter Göran I gren |
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Institution: | (1) The Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA, US;(2) Department of Ecology and Environmental Research, Swedish University of Agricultural Sciences, Box 7072, SE-750 07 Uppsala, Sweden, SE |
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Abstract: | The principle of competitive exclusion is a fundamental tenet of ecology. Commonly used competition models predict that at
most only one species per limiting resource can coexist in the same environment at steady state; hence, the upper limit to
species diversity depends only on the number of limiting resources and not on the rates of resource supply. We demonstrate
that such model behavior is the result of both the growth and biomass turnover functions being proportional to the population
biomass. We argue that at least the growth function should be a nonlinear, concave downward function of biomass. This form
for the growth function should arise simply because of changes in the allometry of individuals in the population. With this
change in model structure, we show that any number of species can coexist at an asymptotically stable steady state, even where
there is only one limiting resource. Furthermore, if growth increases nonlinearly with biomass, the steady-state resource
concentration and hence the potential for biodiversity increases as the resource supply rate increases.
Received 31 August 2001; accepted 10 April 2002. |
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Keywords: | : niche separation competitive exclusion coexistence competition resource limitation species diversity R-star R* |
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