One physical trait that many species show is a variability in the coloration of individuals. This variability may enable individual in a species to blend in better with their specific habitat. If habitat changes over time, individuals with a certain coloration may have a competitive advantage over individuals of another color.
One example of color variation that occurs in Mid-Michigan is among frogs.
The first two photos are both of Green Frogs (Rana clamitans). The first one is of a frog that was living in a wooded wetland - a combination of vernal ponds and deciduous swamp. The floor of this wetland is carpeted with fallen leaves and tends to be a patchwork of light and dark. This frog's mottled colors blend in very well with its background.
|Green Frog #1|
The second photograph shows a Green Frog from a sunny, well-lit permanent pond. Many areas of the pond are covered with a uniform covering of green algae. This frog is a more uniform color, and like the first frog, blends in well with its habitat (but not well enough to avoid being caught with a net and placed on a dock to photograph).
|Green Frog #2|
The next three photographs show Wood Frogs (Rana sylvatica). The first two frogs were found in the same wooded habitat as the first green frog. The first Wood Frog has a very pale coloration with limited variability. Even the stripes on its rear legs and the dark "mask" under its eyes are lighter than in most members of this species.
|Wood Frog #1|
|Wood Frog #2|
|Wood Frog #3|