Research Background: A view of the plants growing in a heated ring. Notice the purple flowers of Centaurea stoebe.

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1 Name Invasion Meltdown: Will Climate Change Make Invasions Even Worse? Featured scientists: Katie McKinley, Mark Hammond, & Jen Lau from Michigan State University Research Background: Humans are changing the earth in many ways, including warming the planet by burning fossil fuels and adding greenhouse gasses to the atmosphere. Scientists have documented rising temperatures across the globe and predict an increase of 3 C in Michigan within the next 100 years. Humans are also changing the earth by transporting species across the globe, introducing them into new habitats. These introduced species may cause problems in their new habitats. Additionally, increasing temperature from climate change may change the way that native and introduced plants and animals interact. All living organisms have a range of temperatures they are able to survive in, and temperatures where they perform their best. For example, arctic penguins do best in the cold, while tropical parrots prefer warmer temperatures. The same is true for plants. Depending on the temperature preferences of a plant species, warming temperatures due to climate change may either help or harm that species. Scientists are concerned that invasive species may do better in the warmer temperatures caused by climate change. Invasive species have been introduced from one area into another, and now thrive in their new habitat. Invasive species harm native species and cause many problems for humans. There are several reasons to expect that invasive species may benefit from climate change. First, because invasive species have already survived transport from one habitat to another, they may be species that are better able to handle change, such as temperature changes. Second, the new habitat of an invasive species may have temperatures A flower of the invasive plant, Centaurea stoebe (spotted knapweed). A view of the plants growing in a heated ring. Notice the purple flowers of Centaurea stoebe. 1

2 Name that allow it to survive, but are too low for the invasive species to do their absolute best. This could happen if the invasive species was transported from somewhere warm to somewhere cold. Climate change could increase temperatures enough to put the new habitat in the species range of preferred temperatures, making it ideal for the invasive species to grow and survive. To determine if climate change will benefit invasive species, scientists at Michigan State University focused on one of the worst invasive plants in Michigan, Centaurea stoebe (spotted knapweed). They looked at Centaurea plants growing in a field experiment with eight rings. Half of the rings were left with normal, ambient air temperatures. The other half of the rings were heated using ceramic heaters attached to the side of the rings. These heaters successfully raised air temperatures by 3 C. At the end of the summer, the scientists collected all of the Centaurea plants from the rings. They recorded both the (1) abundance, or number of Centaurea plants within a square meter, and (2) the biomass (dry weight of living material) of the plants in a square meter as a measure of performance. Scientific Question: How does climate change affect the abundance (number of plants) and performance (size of plants) of the invasive species Centaurea stoebe? What is the hypothesis? Find the hypothesis in the Research Background and underline it. A hypothesis is a proposed explanation for an observation, which can then be tested with experimentation or other types of studies. Scientists collecting data on the plants in the heating rings. 2

3 Scientific Data: Use the data below to answer the scientific question: Treatment Ring # # of Centaurea plants per square meter Dried Centaurea biomass per square meter (g) Ambient Temperature Ambient Temperature Ambient Temperature Ambient Temperature Average For Ambient Temperature Rings Elevated Temperature Elevated Temperature Elevated Temperature Elevated Temperature Average For Elevated Temperature Rings Note 1: Ambient refers to the surrounding temperature (normal, or control), whereas elevated refers to the plants growing in rings with heat added. Note 2: Dried plant biomass per 1 meter square is a good measure of the amount of a plant species in a given area. Calculate average biomass per 1 meter square for ambient and elevated rings and use when graphing below. What data will you graph to answer the question? Predictor variable: Response variables:

4 Below are graphs of the data: # of Centaurea plants per square meter Ambient Temperature Treatment Elevated Temperature Dried Centaurea biomass per square meter (g) Ambient Temperature Treatment Elevated Temperature 4

5 Interpret the data: Based on this evidence, write a statement that helps answer the scientific question. Connect the pattern in the data to a pattern in the natural world. Justify your reasoning using data. Your next step as a scientist: Science is an ongoing process. Did this study fully answer your original question? What new questions do you think should be investigated? What future data should be collected to answer them? 5