Gause’s competitive exclusion principle and “the paradox of the plankton”
713/813 Lecture 6
Gause’s law
Two species competing for the same resource cannot coexist if all other ecological factors are constant
(http://www.ggause.com)
But why are some ecosystems so diverse?
The paradox of the plankton
The problem that is presented by the phytoplankton is essentially how it is possible for a number of species to coexist in a relatively isotropic or unstructured environment all competing for the same sorts of materials
The phytoplankton of which Hutchinson speaks
Prochlorococcus, the most abundant photosynthetic organism on the planet
How is diversity maintained?
• How can a liter of seawater have at least 1,000,000 bacteria and 20,000 bacterial species?
Possible explanations
• Predation and parasitism ‐related tradeoffs
• Frequency‐dependent selection (advantage when rare)
• Resource partitioning and cross‐feeding
• Ecological subdivision (spatial structure, niche subdivision)
• Dispersal creates environmental variability (could speed up evolution)
• Symbioses and co‐evolution
Diversity resulting from predation/parasitism
Diversity: parasitism
With phage
Without phage
Diversity: frequency‐dependence
Diversity: resource partitioning Diversity: resource partitioning Diversity: spatial structure