Interspecific Competition. Topics for this class: What is interspecific competition? What are some mechanisms of competition in nature? What are the outcomes of interspecific competition?
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Topics for this class:
Let’s look at some of these outcomes in lab, field...
Competitive exclusion in Paramecium species
Aerial overview of sage (dark) invading California grassland
Coexistence via niche differences in Joseph Connell’s barnacles; rocky intertidal zone, Europe; based on experimental removals, exclusion cages
Lotka-Volterra model of interspecific competition starts with logistic model, assumes exploitation mechanism; a1,2 = competitive effect of species 2 on 1
-a21 = effect of species 1 on species 2.
-Suppose that it takes two individuals of species two to have the same effect on an individual of species 1 as one ind. of species 1 on species 1; then a12 = 0.5
- this situation defines equation for a line (Y = mX + b)
Francisco Ayala’s test of Lotka-Volterra competition model with fruit flies: model could not work with linear isoclines; this suggests that competitive coefficients change with population densities
Resource level (R)
In this example, species B outcompetes species A because B can drive resources to lower level (it is more efficient at exploiting sparse resources--see previous two slides)