BIO100 Mission Memo for Community Ecology Act 2

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Arizona State University *

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MISC

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Statistics

Date

Feb 20, 2024

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pdf

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Uploaded by sedenig123

Click File → Make a copy in the menu bar to create an editable version of this document. Greetings Fellow Explorer: The situation in the sanctuary has become dire. Not only are the frogcats still sick, the populations of other species might have shrunk or grown unexpectedly. To make matters worse, we witnessed a remarkable kill by an unidentified predator. I completed a genetic analysis of blood cells recovered from the scene of attack, confirming the prey as a grabbins. But a grabbins is an apex predator, which should have no predators of its own. Unless we can discover the cause of these events, the entire community may soon be at risk. Do not despair my human colleagues. We have much data to help us unravel this mystery. For starters, we know that frogcats have been poisoned by boreblasters, which normally do not occupy the same habitat as do frogcats. We also know that boreblasters are virtually absent in their normal habitat. Finally, we collected information needed to evaluate the potential for bottom-up or top-down effects on boreblasters. I am relying on your knowledge and skills to analyze these data and discover the disturbance that caused the boreblasters to disperse. Use the following questions to guide your work: ● Could a change in the abundance of umbrella trees have caused the dispersal of bore-blasters as a bottom-up effect? ● Could a change in the abundance of spotted gliders have caused the dispersal of bore-blasters as a top-down effect? ● Could a change in the diet of a predator explain all of the events observed in the Allurian forest? And if so, which predator do you think has started eating grabbins? The appendices to this mission memo will guide you in answering these questions. Once you have completed your analyses, report your conclusions to me before returning to the sanctuary. You can access the reporting form in Canvas. Do not underestimate the urgency of your work. For the greatest chance of success, upload your report by the due date in your Canvas calendar, 11:59pm, in Tempe, Arizona, United States, Earth. Universally in your debt, The AI 1

Appendix 1 Could a change in the density of umbrella trees have caused the dispersal of boreblasters as a bottom-up effect? We reasoned that a recent change in food supply might have triggered the dispersal of boreblasters. These creatures feed primarily on the woody tissue of umbrella trees; therefore, we need to know whether the density of umbrella trees has either increased or decreased, causing a bottom-up effect on boreblasters (see Figure 1). Figure 1. Left) A food chain for the Allurian Forest depicting the flow of energy and matter. Center) A decrease in the density of umbrella trees should directly cause a decrease in the density of boreblasters and indirectly cause a decrease in the density of spotted gliders. Right) An increase in the density of umbrella trees should directly cause an increase in the density of boreblasters and indirectly cause an increase in the density of spotted gliders. Both scenarios are referred to as a bottom-up effect. Using LiDAR, you constructed a map of the forest and estimated the density of umbrella trees to be 27,000 m 2 of tree tissue per km 2 of land. Now, you must see whether the current density is unusual relative to historical values. Remember, no boreblasters in the sanctuary had never developed into the purple, long-winged form until now; therefore, the density of umbrella trees must be extremely unusual to support our hypothesis. 2

I have provided you with the densities of umbrella trees estimated during previous growing seasons in the sanctuary, all of which occurred before the boreblasters dispersed. Step 1: Make predictions. 1. A ssume that a bottom-up effect caused the dispersal of boreblasters; specifically, a change in the abundance of umbrella trees caused a corresponding change in the abundance of boreblasters. What would you expect to observe when comparing the current density of umbrella trees to the mean historical density? a. We would expect to observe that the current density of umbrella trees is higher than the mean historical density. b. We would expect to observe that the current density of umbrella trees is lower than the mean historical density. c. We would expect to see that there is no difference in current density of umbrella trees than the mean historical density. d. All of the above observations would indicate a bottom-up effect 2. There are two possible claims as to whether a bottom-up effect caused the dispersal of boreblasters, 1) yes, a bottom-up effect caused the dispersal of boreblasters, or 1) no, a bottom-up effect DID NOT cause the dispersal of boreblasters. Two of the bar plots below illustrate what you would expect to observe if a bottom-up effect caused the dispersal of boreblasters. The third illustrates what you would expect to observe if a bottom-up effect did NOT cause the dispersal of boreblasters. Which one would you expect to see if there is no bottom-up effect? a. 3

b. c. 3. If a change in the density of umbrella trees caused the boreblasters to disperse, would you expect the current umbrella tree density to be greater than, less than, or equal to the mean historical density? Pick one of the answers below: a. equal to or less than b. equal to or greater than c. greater than d. less than e. greater than or less than 4

Step 2: Determine whether observed density differs greatly from the expected density. Directions: Our processors have produced the following frequency distribution for the historical density of umbrella trees showing a steady increase with the highest peak at a density between 26624 and 27625 m2/km2 followed by a small decrease in density. The mean historical density is 26994 m 2 /km 2 . Use this to answer questions below. 4. You must determine whether the current tree density is extremely low or high, relative to the historical tree density. Either conclusion would support the hypothesis of a bottom-up effect of umbrella trees on boreblasters. The LiDAR map you created during your recent expedition revealed the current density of umbrella trees to be 27000 m 2 /km 2 . When you compare this to the mean of the historical tree density, you can safely state that: a. the current density is much less than the mean b. the current density is much greater than the mean c. the current density is not much different than the mean 5. You therefore conclude that there is no evidence to suggest that a bottom-up effect triggered the boreblaster surge. a. True b. False Continue to the next section. 5

Appendix 2 Could a change in the density of spotted gliders have caused the dispersal of boreblasters as a top-down effect? We reasoned that a change in predation risk might have triggered the dispersal of boreblasters. Spotted gliders hunt along the trunks of umbrella trees, eating larval boreblasters. Therefore, we need to know whether the density of spotted gliders has either increased or decreased, causing a top-down effect on boreblasters (see Figure 2). Figure 2. Left) A food chain for the Allurian Forest depicting the flow of energy and matter. Center) A decrease in the density of spotted gliders should directly cause an increase in the density of boreblasters and indirectly cause a decrease in the density of umbrella trees. Right) An increase in the density of spotted gliders should directly cause a decrease in the density of boreblasters and indirectly cause an increase in the density of umbrella trees. Both scenarios are referred to as a top-down effect. Using the method of mark and recapture, you can estimate the current density of spotted gliders and compare this density to the density expected from past censuses. I have provided you with the densities of spotted gliders estimated during previous growing seasons in the sanctuary. 6

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