Geography 3251: Mountain Geography Assignment II: Island Biogeography Theory Assigned: May 22, 2012 Due: May 29, 9 AM

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1 Names: Geography 3251: Mountain Geography Assignment II: Island Biogeography Theory Assigned: May 22, 2012 Due: May 29, 9 AM NOTE: This lab is a modified version of the Island Biogeography lab that is offered at Life System and Environmental & Evolutionary Biology course offered at Columbia. Learning Objectives: 1. Learn about the theory of island biogeography. 2. Look at US park species diversity data. 3. Examine how well the theory of island biogeography fits true islands and virtual islands - continental parks. Background:. In the late 1960s, Robert MacArthur and E.O. Wilson came up with a model to explain island species distribution patterns. They thought of things this way. If you start with an island without any life on it, pretty soon individuals of some species will start to reach it. Initially, every individual that reaches the island will be a new species, and so the rate of species colonization will be very high. However, as time goes on, new individuals coming to the island will probably be members of species that have already established on the island, so the species colonization rate will go down, until finally every species around will be represented on the island and the species colonization rate will be 0. At the same time, if we look at the rate of species extinction on the island, this rate will start out at 0, since on an empty island there are no species to go extinct. As the number of species on the island starts rising, the number of species for the island that s the number of species you d expect to find on that island. Figure 1: Graphical depiction of Island Biogeography Theory.

2 In Figure 1, the two lines show how the colonization and extinction rates change as the number of species on the island increases. The place where the two lines cross shows the number of species you would expect to find on the island. Both the species colonization and extinction rates will be affected by the size of the island and its distance from the mainland. The farther an island is from the mainland, the harder it is for species to get there, and so the lower the species colonization rate will be. On the above graph, the colonization line will be moved downward. Smaller islands may be harder to find, so a smaller island might also have a lower colonization rate. A larger island will be able to support larger populations of each species that reaches it, so the chance that a species will go extinct through bad luck will be less on a larger island and the extinction rate should be lower. On the above graph, the extinction line will be moved downward. Similarly, a larger island may have more niches than a smaller island, allowing more species to coexist and so leading to a smaller extinction rate. Part I: The effects of distance and size on species diversity of islands For this exercise we make use of an extensive database on the flora and fauna present in National Parks (NP), National Recreation Areas (NRA), National Monuments (NM), and National Historic Sites and Places (NHS and NHP). You can use this database to test two fundamental aspects of island biogeographic theory: Hypothesis 1-1: Species richness should be a positive function of island size. Hypothesis 1-2: Species richness should be a negative function of distance to the mainland. Instructions: 1. Navigate to the Z:\Geog Files\Hart\GEOG3251\Island and copy the folder to the D: drive. 2. Double click on the Assign2-materials.xlsx to open it in Excel. You will record your data in the spreadsheet labeled data within this file. Note it is important that you do NOT edit any of the cells that are highlighted in yellow. These cells contain formulas. 3. Access the National Park species data bank through the Internet at To gather the data you need, first click a mouse on the name of the park. You will see some cursory information on the park, including its area, then you will see a series of taxon-oriented groups (amphibians, mammals, etc.). If you click on any of these buttons, you will generate a list of all the species in that taxonomic group that occur in the park. This is how you will obtain your two of your key data points: park area and species richness. 4. Select three of the taxonomic groups categorized in the database (reptiles, mammals, birds, fishes, and plants) that you would like to focus on for this exercise. 5. For each island listed on the spreadsheet, record the park size in hectares and the number of species in each of your chosen taxonomic groupings. 6. Then use the measurement tool in Google Earth to assess how close each island is to the closest continental land mass. Record this value in kilometers in the distance to mainland column. These are rough estimates and do not have to be precise!

3 7. To account for the fact that some parks cover a larger percent of the island than others, we ll use the following simplistic correction to estimate the number of species present on the island: Corrected species present = species present / (park area/ island area) These values are calculated for you in the column corrected species in your spreadsheet. 8. Take the natural logarithm of distance to mainland, island area, and the corrected number of species and record these values within the appropriate column in your spreadsheet. Taking the log of these variables makes it more likely that the relationship between species and area and species and distance to the mainland is linear (a requirement of linear regress which we will use later). 9. Graph the natural log of the number of species vs. natural log of island area. Be sure to label your axes and title your graph! 10. Apply trendline to your data. To do so right click on the dataset and select add trendline. Then select linear as the trend/regression type within the type tab. Next go to the options tab and check the boxes next to display equation on chart and display R- squared value on chart. In a linear equation, two parameters, a and b, are estimated for the equation describing the line: Y = a +bx The statistic b describes the slope of the relationship and tells you how much of a change in Y exists for a unit change in X. The statistic a is the Y-intercept and is the value of Y at X = 0. These two statistics uniquely define a line. The R-squared value is a measure of how well the line fits the data. 11. Graph the natural log of the number of species vs. natural log of the distance to the mainland. Again apply a trendline to your data. Be sure that your line of best fit is a linear equation and show both the equation and the r-squared value on your graph Part II: The effects of distance and size on species diversity on continental mountain national parks Hypothesis 2-1: If we compare data from mainland and island parks, the relationships between area and species richness should be positive for both, but the intercepts should be different. 1. Return to the National Park species data bank website ( and select 10 continental parks in mountainous regions. Add the name of these regions to your spreadsheet. 2. Record each park s area in hectacres and the number of species within each taxonomic group you previously selected in Part I. 3. Take natural logarithm of park area and the corrected number of species and record these values within the appropriate column in your spreadsheet.

4 4. Graph the natural log of the number of species vs. the natural log of park area. Again apply a trendline to your data. Be sure that your line of best fit is a linear equation and show both the equation and the r-squared value on your graph

5 Names: Geography 3251: Mountain Geography Assignment II: Island Biogeography Theory Assigned: May 22, 2012 Due: May 29, 9 AM Questions 1. Print out and hand in the three graphs you ve just created. Discuss the general trends seen in these three graphs. Are the trends consistent with the hypotheses? (20 pts) 2. Why should the intercept be lower for the island sites versus the mainland sites? (2 pts)

6 3. What factors do you think underlie the basic pattern of increasing species richness with island area? Continental park area? (5 pts) 4. What is the value of calculating a line through the data? (3 pts) 5. Do you think you would have gotten different results if you had chosen different taxa? Why or why not? (5 pts)

7 6. Surely you observe some noise in the relationships for both the island and the mainland plots. What might account for this noise? (5 pts) 7. How might isolation effects differ among taxa (e.g. amphibians vs. plants)? Why? (5 pts) 8. Do you think it is reasonable to apply the theory of island biogeography to habitat patches or parks on the mainland? Why or why not? What about mountaintops? Are some continental areas more island-like then others? Why or why not? (20 pts)

8 9. Given your results, do you think that scarce conservation funds that could be used to buy a finite amount of land would be better spent to enlarge a small park or a large park (if the goal was to protect as many species as possible)? (10 pts)