Homework Biodiversity and Conservation Biology Populations of a species often live in local areas that have various levels of connection with populations in other areas. If a local population dies out, the area can be recolonized by migration from another area. One of the simplest ways to study processes that lead to localized extinctions (technically called extirpations) is to use small islands. Two scientists, Edward O. Wilson his graduate student, Daniel Simberloff, used tiny mangrove islands off the coast of Florida to study the processes of colonization (typically from the mainland) and extinction on each of these islands. They used insecticides to kill all the arthropods on the islands and then monitored them for new species arriving and, after a species arrived, its future disappearance from the island (and later possible recolonization). This was done to test a theory about the effects of distance of an island from the mainland and island size on rates of colonization and extinction. In this homework assignment, you will use a simplified computer model to view how this works. Go to the site: http://virtualbiologylab.org/ModelsHTML5/IslandBiogeography/IslandBiogeography.html by clicking on the link within the assignment on CANVAS or copying and pasting above link. Read through the Background Information and Tutorial material, using the image of a house (home button) to return to the main page when needed. First, you are going to collect some starting (benchmark) data that you can use for comparison when you start to change things in the experimental set-up. I. Simulation # 1: Click on Run Experiments from home page. Notice that your 2 islands are both 10 km from the mainland and 256 km wide. These are Tropical islands and we are studying terrestrial arthropods (insects, spiders, ). Click on the To Data arrow at the bottom right. You are going to collect data on # individuals on each island (large table at top left) and average number of species per island (small table at lower right). You are going to run the model with these settings 5 times (to get average values). Each time you run the model, you will let it go to a run time of 500. Directions: Stop the model by clicking the stop button at lower right (button with 2 vertical lines). Click clear islands and reset average (blue buttons). Then, click the start button (large right pointing arrow at lower left). Watch the run time and click the stop button when it gets to a run time = 500. Note that you can speed up the model by clicking the button to the right of start/stop. After running the model once, fill in your data in the table on the next page, then clicking clear islands and reset average and running it again. Run it for a total of 5 times, writing down your data each time. Finally, calculate the averages for your five runs. NOTE: The two pieces of data you will record are Total # Individuals = Island Total (last row in 2 columns of data) and Average # species (from small box on lower right of screen). To calculate an average for a column, add up the five values in that column, then divide by 5. Table 1: Both islands 10 km from mainland; island size = 256 km diameter; run time 500 Island 1 Total # individuals Island 1 Avg. # Species Island 2 Total # individuals Island 2 Avg. # Species Trial # 1 Trial # 2 Trial # 3 Trial # 4 Trial # 5 Average for each column Note that this data shows you how much variability there is in the data for the 2 islands due purely to chance (since the relevant variables were all set to identical values). II. Simulation # 2: Click on the arrow at the bottom right called To Design For this simulation, you are going to alter the distance from the mainland for one of the islands and see how this affects both total # individuals and average # species. Using the arrows, for island # 2, increase the Island distance (km)) to 410 km, the maximum allowed in the simulation. Run this model 5 times and fill in your data in the table below. Use the directions from simulation 1 if you have forgotten how to do any of the steps Table 1: Island 1, 10 km from mainland; Island 2: 410 km from mainland; island size = 256 km diameter for both islands. Run time = 500 Island 1 Total # individuals Island 1 Avg. # Species Island 2 Total # individuals Island 2 Avg. # Species Trial # 1 Trial # 2 Trial # 3 Trial # 4 Trial # 5 Average for each column What differences did you notice, both as you watched the process of colonization and extinction, and based on what you see in the data? Be specific. _____________________________________________________________________________________ _____________________________________________________________________________________ What do you think was the biggest impact of distance from the mainland? _____________________________________________________________________________________ III. Simulation # 3: Click on the arrow at the bottom right called To Design For this simulation, you are going to alter the size of one island and see how this affects both # individuals and average # species. Using the arrows, set Island distance (km)) to 110 for both islands AND set Island diameter to 64 for Island 2 (leave it at 256 for island 1). Run this model 5 times and fill in your data in the table below. Use the directions from simulation 1 if you have forgotten how to do any of the steps Table 1: Both islands, 110 km from mainland; island size: Island 1: 256 km2 ; Island 2: 64 km2 Run time = 500 Island 1 Total # individuals Island 1 Avg. # Species Island 2 Total # individuals Island 2 Avg. # Species Trial # 1 Trial # 2 Trial # 3 Trial # 4 Trial # 5 Average for each column What differences did you notice between the 2 islands, both as you watched the process of colonization and extinction, and based on what you see in the data? Be specific. _____________________________________________________________________________________ _____________________________________________________________________________________ What do you think was the biggest impact of island size? _____________________________________________________________________________________ IV. Simulation # 4: Design your own simulation to test something. For this simulation, figure out something you want to test, set it up and run it. Dont make it too complicated or it will be difficult to interpret your results. Provide a detailed explanation of what you did, a table with your data, and your results below

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