Keywords
paradox of plankton, species diversity, coexistence, lattice model, paradox of enrichment
Start Date
1-7-2004 12:00 AM
Abstract
In aquatic ecosystems, species diversity is known to be higher in poor nutrient conditions. Theenrichment of nutrition often induces the loss of biodiversity. This phenomenon is called the paradox ofenrichment, since higher nutrient levels can support more species. Furthermore, the species diversity isusually high in most natural communities of phytoplankton. However, the niches of planktonic algae seemalmost identical in apparently homogeneous, aquatic environments. Therefore, the high species diversity ofphytoplankton is incomprehensible and called the paradox of plankton. Mathematical studies show that localcoexistence of competitive species is rare. In a competitive community, the most superior species eliminatesall the inferior species in the long run. Experimental results using chemostats also support this theoreticalprediction. Thus we have no sound explanation for the local coexistence of many planktonic species in lownutrient conditions. Here we build a lattice model of ten planktonic species. All ten species are undercompetition for space in a relatively large lattice space. We report a few cases of simulation run. Simulationshows that, in an ecological time scale, coexistence of many species is observed when all species have lowidentical birth rates. We also show that, when the average birth rates are high, the most superior speciesexclude all the inferior species immediately. Our results suggest that competition for space does not functionamong species, when the densities of species are extremely low. The results of current simulationexperiments may be related to the paradox of enrichment as well as that of plankton.
The Coexistence of Plankton Species with Various Nutrient Conditions: A Lattice Simulation Model
In aquatic ecosystems, species diversity is known to be higher in poor nutrient conditions. Theenrichment of nutrition often induces the loss of biodiversity. This phenomenon is called the paradox ofenrichment, since higher nutrient levels can support more species. Furthermore, the species diversity isusually high in most natural communities of phytoplankton. However, the niches of planktonic algae seemalmost identical in apparently homogeneous, aquatic environments. Therefore, the high species diversity ofphytoplankton is incomprehensible and called the paradox of plankton. Mathematical studies show that localcoexistence of competitive species is rare. In a competitive community, the most superior species eliminatesall the inferior species in the long run. Experimental results using chemostats also support this theoreticalprediction. Thus we have no sound explanation for the local coexistence of many planktonic species in lownutrient conditions. Here we build a lattice model of ten planktonic species. All ten species are undercompetition for space in a relatively large lattice space. We report a few cases of simulation run. Simulationshows that, in an ecological time scale, coexistence of many species is observed when all species have lowidentical birth rates. We also show that, when the average birth rates are high, the most superior speciesexclude all the inferior species immediately. Our results suggest that competition for space does not functionamong species, when the densities of species are extremely low. The results of current simulationexperiments may be related to the paradox of enrichment as well as that of plankton.
