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Biol 106 Ecology Modeling Lab – Fender's Blue Butterflies

Introduction

Global biological diversity (the variety of organisms living in the biosphere, the global ecosystem) is vast, with over 1.8 million described species and estimates of more than 10 million species not yet discovered. Some ecosystems, like tropical rain forests, support large concentrations of species. Many of these species may go extinct before they are ever discovered, due to a variety of factors affecting the distribution of species within populations, communities and ecosystems. The study of the interactions between these organisms and their environment is called ecology. Ecology integrates multiple disciplines of biological research, where scientists study the interactions of organisms in the environment from a variety of hierarchical levels, including organismal ecology (study of individuals), population ecology (study of groups of individuals of the same species) and community ecology (study of groups of populations of different species in an area) to name a few. Identifying factors affecting species distributions allows biologists to work to preserve our current biological diversity. Conservation biology integrates ecology, physiology, molecular biology, genetics, and evolutionary biology to preserve biological diversity at all levels. Each species has an ecological niche, that is, the combination of biotic and abiotic factors required for the species to exist. Over evolutionary time ecological niches change and species either respond to change (e.g., via natural selection) or go extinct. This pattern is a natural phenomenon occurring since life first evolved; however, the current rate of species extinction has increased due to human activities. Species require specific habitats (areas that support a specific group of species) for survival and reproduction, but human activity has directly or indirectly altered or even eliminated the habitats of many species. For example, farms, cities and roads have reduced the size of species’ habitats, limiting populations to small isolated habitats called fragments. The fragmentation of existing habitat into smaller patches does more than simply reduce the available habitat area available for populations. Edges of habitat fragments are often of lower quality than the interiors of habitat fragments, because the edges of a habitat are influenced by its surrounding landscape. For example, pesticides and other agricultural products are more likely to drift into the edge of the habitat than into the interior, and weeds are more likely to immigrate to the edge of the habitat from surrounding fields or road cuts. Therefore, what factor should an ecologist minimize when conserving habitats? In an effort to preserve species severely affected by human activity, such as endangered species (a species in danger of extinction throughout all or a significant portion of its range), biologists have developed the field of restoration ecology. In this field, ecological principles are used to return disturbed ecosystems to conditions as similar as possible to their natural state.

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In today’s lab we will discuss the biology of an endangered butterfly species call the Fender’s blue butterfly (Icaricia icarioides fenderi), a species native to the prairies of western Oregon and southwestern Washington. Specifically we will use a computer simulation to examine possible strategies to save the Fender’s blue butterfly through restoration of its fragmented prairie habitat. Fender’s blue butterfly In the last century, farms, cities, and roads have replaced most of the native prairie habitat in western Oregon and southwestern Washington. Today, less than 1% of the indigenous prairie remains, distributed in isolated patches that are often separated by several kilometers. Among the species that live in the prairie habitat is the Fender’s blue butterfly. This is a small butterfly, with a wingspan of about two centimeters (about one inch). Females have rusty brown wings and males have iridescent blue wings, which gives the butterfly its name. The Fender's blue butterfly requires native prairie species for nectar and larval food sources. Because of the reduction in prairie habitat, the Fender’s blue butterfly is in danger of extinction (and up until 1989 it was believed to be extinct). Less than 4000 of these butterflies are left in western Oregon and southwestern Washington. The government and other private agencies are willing to attempt to save the Fender's blue butterfly by restoring old farmlands and other abandoned areas to butterfly habitat. Habitat restoration is quite costly (estimated cost for restoring populations of Fender’s blue butterfly by 2033 is around 16 million dollars) and requires hours of manual labor (removing unwanted non-native species and adding native species). Because the restoration process is time consuming and expensive, ecologists must first identify which areas of land would have the highest impact in restoring the population of Fender’s blue butterflies. Ecological models allow ecologists to compare a variety of possible restoration plans to determine the best possible strategy for the time and money allotted to a project.

Exercise: Funds are available to restore 200 acres of native prairie habitat necessary to allow populations of Fender’s blue butterflies to recover to stable levels. Your job is to use a modeling program to determine the best way to distribute the 200 acres of restored prairie in order to maximize the number of populations of Fender’s blue butterflies. Possible ways to distribute restored land: . • Make existing patches of prairie larger. . • Make corridors connecting existing patches of prairie. . • Make a series of small patches (stepping-stones) between the larger ones. . • Use combinations of the above or try something completely different!

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Directions for running the program

1. Click on the Ecobeaker icon in the dock (beaker with tree coming out the top). 2. Go to the Labs pull down menu at the top, choose butterflies 3. Go to the Markers pull down menu. It lists different habitat scenarios. First choose

100 years ago. You will use the Marker pull down menu several times throughout this lab.

Simulation 1: 100 yrs Ago To start the simulation click on the green arrow on the bottom left of the screen

or select the Action pull down menu and choose Go. Let the simulation run for a total of 700 weeks. You can observe the number of weeks the simulation is running on the bottom of the screen. You can also adjust the speed of the simulation (Slider bar at the bottom of the screen) by clicking and sliding the speed bar. In order to stop the simulation at 700 weeks, slow the simulation down, once it gets close to 700, then stop by clicking on the stop icon or selecting the Action pull down menu and choose Stop. Note that this is an annual population so every year (52 weeks) it starts over.

Run this simulation 1 time. After your simulation, RECORD the number of

butterflies in the population after 700 weeks in Table 1 below (The number of remaining butterflies can be found in the Statistics box). Share your data with the other lab tables.

Simulation 2: Today (Baseline Data) Today represents the remaining habitat currently available for the butterflies. Go

to the Markers pull down menu. Choose Today. You will notice the farmland habitat is the most prevalent and the prairie remnants are quite small. Your total Area of Prairie is 800 acres (Located in the Statistics box).

Run this simulation 6 times. After each simulation, RECORD the number of

butterflies in the population after 700 weeks in Table 1 below (The number of remaining butterflies can be found in the Statistics box). Make sure to RESET for each simulation. To reset: select the Action pull down menu, choose reset or choose the reset icon at the bottom of the screen (icon to the right of the stop icon).

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Simulations 3 – 8: Possible Methods of Habitat Restoration Simulation 3 = Patch Expansion (increase the size of the patches) Simulation 4 = Corridors (directly connect habitats)

Simulation 5 = Stepping stones (connect patches by small patches rather than continuous corridors)

Simulations 6, 7, 8 = Create your own models (A, B, & C). Try to create models that will generate the largest population of Fender’s blue

butterflies! For above simulations (3 - 8) you will be adding new prairie habitat. You may

only add an additional 200 acres of prairie, making the total prairie habitat = 1000 acres.

To make a new habitat, first reset the simulation using the reset icon to the right

of the stop icon. Then go to the Action pull down menu, choose Paint, then choose Prairie in the Habitats box. This converts the mouse into a "paint" tool so you can "paint" prairie habitat. If you add more than 200 acres, you can remove the excess by choosing Farmland in the Habitats box and removing some prairie. After you finish painting each prairie habitat, save your newly painted habitat before you run a simulation, so you can run the same simulation 6 times.

Saving new habitats: Go to the Marker pull down menu, choose Add Marker

(name your marker something that corresponds to the simulation you are running, for example if you just created a Patch expansion name the new habitat Patch). After the new habitat is saved you can now run the simulation.

Run the simulation 6 times, for 700 weeks each and record the data in

Table 1 below Note: To run multiple simulations for new habitats, you will reset, go to the Marker pull down menu and select your newly saved habitat (i.e., Patch). For simulations 3-8 also provide a drawing (map) of each new habitat you create in the spaces provided at the end of this lab write-up.

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Table 1. Fender’s Blue Butterfly population sizes for various habitat models. Trial # Number of Surviving Butterflies in each Model Habitat

100 yrs ago

Today (Baseline)

Patch Expansion

Corridors Stepping Stones

Model A Model B Model C

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2

3

4

5

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Average of all trials for each model

Conclusions: On average, which of the above habitat models resulted in the most surviving butterflies? Explain why you think that model worked the best. In your answer, include other factors that should also be considered before implementing the best model. Be thorough, there’s a lot of time and money associated with your habitat restoration decision!

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Maps of Prairie Habitat Models

Model A Model B Model C

Patch Expansion Corridors Stepping Stones