Mixing of Supersaturated Assemblages and the Precipitous Loss of Species

Mechanisms influencing species richness are many. Recent theoretical research revealed additional mechanisms that involved neutral and lumpy coexistence and alternating assemblage states. These mechanisms can lead to conditions where the number of coexisting species is greater than the number of lim...

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Bibliographic Details
Published in:The American naturalist 2008-02, Vol.171 (2), p.162-175
Main Authors: Roelke, Daniel L., Eldridge, Peter M.
Format: Article
Language:English
Subjects:
Algae
Animal and plant ecology
Animal migration behavior
Animal, plant and microbial ecology
Aquatic ecosystems
Biodiversity
Biological and medical sciences
Cichlidae
Extinction, Biological
Fundamental and applied biological sciences. Psychology
General aspects
Hydraulics
Lentic systems
Likelihood Functions
Modeling
Models, Biological
Periodicity
Phytoplankton
Phytoplankton - physiology
Plankton
Population Density
Population Dynamics
Simulations
Species
Supersaturation
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Summary:Mechanisms influencing species richness are many. Recent theoretical research revealed additional mechanisms that involved neutral and lumpy coexistence and alternating assemblage states. These mechanisms can lead to conditions where the number of coexisting species is greater than the number of limiting resources, that is, species supersaturation. Our research focused on the role of disturbances (migration and pulsed through‐flows) in supersaturated plankton systems. Our simulations employed 30 different supersaturated assemblages generated by using various ecological principals. Our findings indicated that immigration rates as low as 0.1% of total biomass per day generally led to regional homogenization of species and dramatic extinction events, with assemblages characteristic of lumpy coexistence being more resilient than those characteristic of neutral coexistence or alternating states. Generally, pulsed through‐flows tended to offset, to some extent, the negative effects of migration. The precipitous loss of species with the onset of migration is observed in other systems as well, for example, cichlid fish communities of East Africa rift lakes and songbird assemblages from Indian Ocean islands. While many explanations have been offered to explain postimmigration extinctions in species‐rich systems, another explanation might be that the assemblages in these systems are in a fragile state of supersaturated coexistence.
ISSN:0003-0147
1537-5323
DOI:10.1086/524955