SEE-UAtlantic Forest

Exercise 3: Natural Selection/Evolution: Ecotypic Variation
Module 3: Natural Selection and Evolution


Your Questions

  1. How are ecological gradients defined?
  2. 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

  1. Compare two or more populations of the same species along an environmental gradient.

Methodology

  1. Task A—Recognition of local environmental gradient
  2. Task B—Measurement of effects
  3. Task C—Data analysis and write up

Objectives

  1. Present concepts of ecological gradients
  2. Introduce the concept of natural selection
  3. Introduce basic techniques for statistical analysis of data

Key Skills

  1. Learn how to identify environmental gradients on a local scale
  2. Recognize differences among populations
  3. Basic statistical analysis

Timetable

Total time—1 day

  1. Morning
  2. Afternoon

Materials Needed

  1. Field notebook and writing equipment
  2. Tape measures (50 m)
  3. Compass and GPS
  4. Collection equipment for studied species
  5. Flagging, stakes, string