Analyze the scenarios of competition between the Colorado pike minnow and rainbow.|medicine
Competitive Exclusion
Instructions: Use the competition model (contained in “competition model.xls”) to evaluate the scenarios of competition between the Colorado pike minnow and rainbow. For each scenario, use the Excel sheet to enter the values for K, r , and the competition coefficient (α or β) for each population..
As per usual, you will need to work through this assignment in order to successfully answer the day’s clicker questions.
Abbreviations:
Species/population 1 = pike minnow
Species/population 2 = rainbow trout
α = effect of species 2 on species 1
β = effect of species 1 on species 2
1. You work for the US Fish and Wildlife Service, which wants to maintain populations of endangered fish in the Colorado River. As a wildlife manager, you know that the population of pike minnow is threatened by non-native trout. How might you increase pike minnow populations? Brainstorm two potential ideas, and explain how each plan targets r, K, α, or β.
2. As part of your Fish & Wildlife job, you measure some populations and find the following: the competitive effect of trout on pike minnows equals 1.25, the competitive effect of pike minnows on trout equals 0, the per capita growth rate of pike minnows equals 0.25, and the per capita growth rate of trout equals 0.5. The carrying capacity of a species equals the number of available nesting sites. Currently, the environment contains 500 nesting sites.
You devise a way to introduce artificial nesting, which only pike minnows can use. If you introduce these artificial nesting sites (leaving the trout nesting sites at 500), how many will you need for the pike minnow’s population to grow?
a) 600
b) 700
c) 800
d) 900
e) 1000
3. Your supervisor makes you remove all of the artificial nesting sites because they are preventing people from rafting on the river. So you decide to save the population of pike minnows by destroying trout nesting sites instead. Assume that 500 natural nesting sites exist for pike minnow and 500 exist for trout. At what number of trout sites will the pike minnow population start to grow? Assume that competition coefficients and per capita growth rates are the same as in question 2.
a) 450
b) 400
c) 350
d) 300
e) 250
4. After leaving the Fish & Wildlife Service, you land a job as a botanist on islands off the coast of California. You are studying an endangered plant species that only grows there and nowhere else in the world. You find these plants are outcompeted by an introduced species from Europe.
You study the populations and find the following conditions:
Species
Carrying capacity (K)
Growth rate (r)
native plant
200
0.5
invasive plant
500
0.5
One reason native plants are declining is that the invasive plants absorb nitrogen from the soil about twice as fast (α = 2). How low must you reduce this competition coefficient to enable the native species to persist? Assume that the native species has no competitive effect of the invasive species (β= 0).
a) 1.5
b) 1.25
c) 1.0
d) .75
e) .25
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