Lecture 24

Lecture 24 - Often, if the two species share some but not...

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Often, if the two species share some but not all resources, there is no way in which one species can become so numerous that it drives out the second species. It is this fact that leads to the coexistence of different species in the same ecosystem, even though they share some components of their ecological niches. If the product of α 21 and α 12 is less than one, so that there are unique resources available to each species and the competition between the two species is low, then the total numbers of the two species that can live together in an ecosystem is larger than the numbers of both species that could live separately. Such a situation is shown in the figure below, in which K 1 = 300, K 2 = 300, α 21 = 0.5, and α 12 = 0.5. The numbers of each species that can occupy the ecosystem alone are 300, but the total carrying capacity is 400 (200 of each species) when both species are present and the competitive interactions have led to an equilibrium. Provided that α 21 and α 12 do not change, the two species may persist indefinitely. 200 + 200 = 400 individuals of the two species can coexist at equilibrium Numbers of species 2 Numbers of species 1 K 1 / α 12 K 2 / α 21 If species 2 could reach 600, then species 1 would be driven to zero If species 1 could reach 600 then species 2 would be driven to zero Shaded area shows the total number of individuals possible How competition coefficients can lead to a stable equilibrium
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This note was uploaded on 07/13/2009 for the course BILD BILD3 taught by Professor Henterheather during the Spring '08 term at UCSD.

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Lecture 24 - Often, if the two species share some but not...

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