Homework Assignment #6: Competition

Due: Monday, 30 October 2006

NOTE: You will need graph paper for this assignment, which will be attached to this sheet!

1. You are studying two species of Costa Rican hummingbirds, the white-bellied mountain-gem (species 2) and the green-crowned brilliant (species 1), on the Caribbean slope of the Cordillera de Talamanca.  For the green-crowned brilliant, K₁ = 100 and a = 2, and for the white-bellied mountain-gem K₂ = 150 and b = 3.

            A. Initial population size is N₁ = 25 for green-crowned brilliant and N₂ = 50 for

                 the white-bellied mountain-gem.  Graph the state space and isoclines for each species,

                 and plot these initial population sizes.

            B. Predict the short-term dynamics of the populations based on the isocline placement.

            C. What is the final outcome of interspecific competition?  Is this a stable equilibrium?

2. If two species have the following competition coefficients, a = 0.9 and b = 0.5 with carrying capacities of K₁ = 100 and K₂ = 250, plot out the isoclines on a state space graph.

            A. When the populations are at N₁ = 25 and N₂ = 150, what are the short-term dynamics

                 of the populations?

            B. If the populations were at N₁ = 125 and N₂ = 150, what are the short-term dynamics of

                the populations?

            C. What if the populations were at N₁ = 120 and N₂ = 250?

            D. Will competitive exclusion occur in this environment given the above data? Why or

                 why not?

Compare and contrast (Make sure that you give a comparison as well as a contrast)

3.  Fundamental niche vs. realized niche.

4. Interference competition vs. exploitative competition.

5. Define the competitive exclusion principle.

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