Methods
SamanthaJa
Reading_PatchyPrairies.docxMethods and Data Collection: “Patchy Prairies”
A population is a set of individuals of the same species living in a given region or habitat. Ecologists employ a variety of methods to study the structure of populations, including simulation models. Due to cost and time, scientists are not always able to perform long-term, large-scale monitoring projects on animal and plant populations. However, they can perform smaller field and laboratory experiments that inform our knowledge of the organism’s natural history, behavior, and ecology. Based on our previous knowledge, scientists can create “rules” for how a system should function. When the model runs, it simulates how the system functions. By changing variables within these rules, scientists can predict how populations, communities, ecosystems, and more may function under different conditions.
Example: If we were modelling whether an animal population in South Florida can recover after a hurricane, we would want to include rules on how often hurricanes affect the area, the population size before the hurricane, the survival probability of different age classes in that animal population, what happens to the animal’s food source after the hurricane, what happens to the animal’s reproduction (e.g., number of offspring), etc. The model would take this information and simulate whether the animal population would decline, stay the same or increase.
In this week’s lab, you will use SimBio’s “Patchy Prairies” module to simulate an experiment in population ecology. Your TA will guide you through basic concepts required to understand the experiment and will help you collect your own individual data for the write-up. Takes notes throughout the lab class on your experimental methods, which will help you complete this week’s assignment that focuses on drafting the “Methods” section of your write-up.
Background: “Patchy Prairies”
Download SimBio to your desktop. Open the application and go to “Ecology”, then “Patchy Prairies”. Launch the module and download the workbook. Read the following REQUIRED passages from the workbook. (Your TA will quiz you on information and concepts covered in the required passages.)
Introduction: pages 1-2
Ecological knowledge included in the simulation model: page 5
Exercise 4 Connections: page 18
You are welcome to play with the simulations in the virtual lab, but you are not required to complete any of the workbook exercises before class. Your TA will be going over the modelling and simulations specific to this course during class time.
Island Biogeography
In 1963, MacArthur and Wilson proposed a model of island biogeography to explain the number of species on an island. The number of species depends on the probability of colonization (animals and plants arriving from another island or the mainland) and the probability of extinction (animals and plants die without being replaced), which in turn depends on how close the island is to the mainland (or another island) and the size of the island. Animals and plants from the mainland are more likely to colonize an island if it is close by than far away. Larger islands can also support more colonizing animals and plants because there is more room and more diverse habitats. Smaller islands have less available habitat and less available resources, so animals and plants have a more difficult time surviving (i.e., higher extinction rate). Additionally, small populations are at a higher risk of extinction due to random events. Thus, the model predicts that islands that are large and close to a mainland will have more species than an island that is small and far away from the mainland.
Patches of prairie within a non-prairie environmental landscapes can be thought of as “islands”. In conservation, whether a population survives or goes extinct depends on the size of the island (patch) and how close the island (patch) is to another patch. In this week’s virtual lab, you will see how habitat patches can follow island biogeography theory. Based on this theory, consider: Will patches that are closer together or further apart have higher butterfly population sizes? Will patches that are smaller or larger have higher butterfly population sizes?
Experiment
River Ridges Preserve is a preserve in the Willamette Valley of Oregon with patches of native prairie habitat that support Kincaid’s Lupine plant and Fender’s Blue Butterfly populations. A conservation group called the Rivers to Ridges Partnership was recently granted a large swatch of land from a developer to connect the River Ridges Reserve patches. River Ridges Reserve has invited you to model three possible conservation strategies (patch enlargement, corridors, and stepping stones). You will assess which of these habitat restoration configurations would increase the size (and thus the stability) of the Fender’s butterfly population compared to their current reserve set-up.
The reserve has a problem with invasive plant species, so they are investigating past use of fire suppression techniques to maintain native prairie habitat. Fire management wants to begin using periodic prescribed burns to restore natural prairie habitat. Based on work with other species, they claim that the best habitat conservation strategy is stepping stones. You will assess whether stepping stones will be effective in maintaining or improving the size and stability of Fender’s Blue Butterfly populations during prescribed burns.
References
MacArthur, R.H. and E.O. Wilson. 1963. An equilibrium theory of insular zoogeography. Evolution 17(4):373-387.
SimBio Virtual Labs. 2019. Workbook: Patchy Prairies.
