Wle200 Interspecific Competition

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Interspecific Competition

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an interaction between 2 or more species over a limiting resource that results in a decrease in population size or fitness of 1 of the species

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Types of Competitive Interactions

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-Consumptive (exploitative) – using resources
-Preemptive – (exploitative) using space
-Overgrowth – (exploitative) one species growing over another, blocking light or other resource
-Chemical –use of toxin…allelopathy in plants
-Territorial – (interference) fighting or exhibiting other behavior in defense of space
-Encounter – (interference) transient interaction directly over resources

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Lotka-Volterra Equation for Competition

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****See slide 5!*****

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Gause’s Competitive Exclusion Principle

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experimentation with paramecium
-Assumes potential competitors have exact same resource requirements
-Assumes environmental conditions remain constant

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Unstable Equilibrium

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--either can dominate
--each species inhibits growth of other species more than its own
--generally determined by which species is most abundant at outset

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exploitative competition

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competition by a group or groups of organisms that reducces a resource to a point that adversely affect other organisms

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Interference competition

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Competition in which access to a resources is limited by the presence of a competitor

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Exclusion

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One species will out-compete the other

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Stable Equilibrium - Coexistance

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--neither excludes the other
--each species is inhibited more by its own growth, than by that of the other species

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Role of Temporal Variation of Environment on Possible Competition

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--dominance of grasses in
African savannah varied
with changes in rainfall
during rainy season

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NICHE

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--functional role of an organism

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fundamental niche

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= total range of environmental conditions under which an organism can survive

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realized niche

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= portion of fundamental niche that is still available when potential competitors are present

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Niche Width

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--sum total of different resources used by an organism