The POPULUS modelling software
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Transcript of The POPULUS modelling software
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The POPULUS modelling software
Download your copy from the following website (the authors of the program are also cited there). This primer is best used with a running POPULUS program.
http://www.cbs.umn.edu/populus/
The opening screen is shown below (this primer is based on Java Version 5.4)
Main Menu bar – gives access to major program features
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The POPULUS modelling software
Depending on your screen size, you may need to adjust the POPULUS program windows. Each of them can be scaled by clicking-and-dragging on any edge (just like any other window).
POPULUS windows may be scaled by clicking-and-dragging on any edge.
POPULUS windows may be repositioned by clicking-and-dragging on their heading.
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The POPULUS modelling software
A Help document can be accessed by clicking on the Help button in the menu bar. The help document is a pdf file and will require a pdf reader.
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The POPULUS modelling software
Access the models by clicking on the Model button. We’ll discuss Lotka-Volterra competition models in this section.
NOTE: This primer assumes that you have mastered the lesson(s) on:• Density-Independent growth models• Density-Dependent growth models• Lotka-Volterra competition (co-existence model)
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
We have seen from the previous models that if two species are equally competitive, they will co-exist. Now we look at the scenario in which they are not equally competitive but in such a way that each species has a good chance of winning the competitive interaction and driving the other species to extinction. Let’s start from the situation in which Species 2 has an overwhelming K2. Input the following parameters and generate the N2 vs N1 plot. Recall that 1E3 is scientific notation for 1,000.
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
The resulting graph is shown below. To give Species 1 a better chance of winning, let’s increase β (effect of Species 1 on Species 2). Biologically speaking, we are making Species 1 better able to find food, water and shelter at the expense of Species 2. The following graphs show the changes in the competition dynamics.
As expected, Species 2 will always win in this scenario because of its overwhelming K2. It can maximize its environment better than Species 1. But what will happen as β increases?
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
β = 1.0
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
β = 2.0
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
β = 4.0
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
β = 8.0
The area (encircled) in which Species 1 grows while Species 2 dies increases as β increases. This is as expected since Species 1 is becoming a more able competitor.
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
By doing a vector analysis, one can see that the outcome of the competitive interaction depends on the initial abundance of the competitors. The following graphs show these.
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
Plot these graphs in your POPULUS program by changing the initial abundance of the two species.
N1(0) = 50 N2(0) = 600
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
Plot these graphs in your POPULUS program by changing the initial abundance of the two species.
N1(0) = 70 N2(0) = 700
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
Plot these graphs in your POPULUS program by changing the initial abundance of the two species.
N1(0) = 200 N2(0) = 800
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
Plot these graphs in your POPULUS program by changing the initial abundance of the two species.
N1(0) = 100 N2(0) = 400
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
Plot these graphs in your POPULUS program by changing the initial abundance of the two species.
N1(0) = 50 N2(0) = 100
![Page 17: The POPULUS modelling software](https://reader038.fdocuments.net/reader038/viewer/2022103007/56814369550346895dafe6eb/html5/thumbnails/17.jpg)
The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
Plot these graphs in your POPULUS program by changing the initial abundance of the two species.
N1(0) = 10 N2(0) = 200
![Page 18: The POPULUS modelling software](https://reader038.fdocuments.net/reader038/viewer/2022103007/56814369550346895dafe6eb/html5/thumbnails/18.jpg)
The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
Now let’s take a look at the N vs t plot for N1(0) = 10 and N2(0) = 200.
This plot shows a very clear win for Species 2. We can see its growth curve reaching a resultant K2 of ~1000 while that of Species 1 hit zero (recall concept of x-intercept).
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The POPULUS modelling software: Lotka-Volterra Competition (Either species may win; co-existence is not possible.)
The N vs t plot for N1(0) = 50 and N2(0) = 100 however, has a different story.
This plot predicts a win for Species 1 with Species 2 putting up a good fight in the beginning. Now, if you were a conservationist intent on preserving Species 2, one option open to you would be to cull (trim as in ‘kill the excess’) the Species 1 population before they can outcompete Species 2. Culling can be done at Time 10 as the model predicts (see dashed line).
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The POPULUS modelling software: Lotka-Volterra Competition
We end our discussion of the Lotka-Volterra Competition models where either species may win and co-existence is not possible. To continue, you must download the other models from the ESIII blog.