SEE-U 2000: Atlantic Forest - Module 3:Exercise 3

Exercise Contents:

• | Your Questions
• | Background
• | Your Assignment
• | Methodology
• | Objectives
• | Key Skills
• | Timetable
• | Materials Needed

Exercise Contents:
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# Atlantic Forest ## Exercise 3: Natural Selection/Evolution: Ecotypic Variation Module 3: Natural Selection and Evolution
Printer format ### Your Questions How are ecological gradients defined? How do local populations respond to ecological gradients? ### Background Ecotypes are local populations that differ genetically in adaptations or responses to environmental conditions. Ecotypes are also known as races or ecological races. The traits showing ecotypic variation can be either morphological or physiological. Not all differences between populations are ecotypes since some differences are simply the result of the response of a given genotype to different environmental conditions. Both genotypic and phenotypic plasticity are important for species that live in habitats that vary spatially or temporally. If the differences between or among populations are not genetically based, but due to plasticity of response of the organisms, then the populations are called ecophenes or phenecotypes. An ecological gradient can be defined as a change in an environmental factor, such as water availability, soil pH, salinity, temperature, over a specified distance. However, this distance may be measured in centimeters or thousands of kilometers depending on the scale of the study. In the site we will be studying we will use a gradient based on water availability. ### Your Assignment Compare two or more populations of the same species along an environmental gradient. ### Methodology Task A—Recognition of local environmental gradient Identify a local environmental gradient Select a species distributed along the gradient Select traits for measurement Task B—Measurement of effects Establish sampling points along the gradient Collect individuals at each sampling point and measure the traits previously selected. Task C—Data analysis and write up Data entry into computer Analyze the data Compare the populations Summarize results for presentation (written and oral) ### Objectives Present concepts of ecological gradients Introduce the concept of natural selection Introduce basic techniques for statistical analysis of data ### Key Skills Learn how to identify environmental gradients on a local scale Recognize differences among populations Basic statistical analysis ### Timetable Total time—1 day Morning Localize an environmental gradient Identify a species with a distribution over the gradient. Collect and measure individuals at various points along the gradient Afternoon Terminate data collection, if necessary Data entry and analysis Write up report ### Materials Needed Field notebook and writing equipment Tape measures (50 m) Compass and GPS Collection equipment for studied species Flagging, stakes, string