Color Evolution Leads to Better Survival for Moths

The peppered moth as it looked before the Industrial Revolution and also now that clean-air laws have improved pollution in the United Kingdom. (Olaf Leillinger via Wikipedia)

(CN) – Moths that have evolved to be a paler color are less likely to be eaten than the darker moths that have adapted to air pollution, a British study found.

In “one of the most iconic examples of evolution,” researchers have found peppered moths adapted to air pollution from the Industrial Revolution, and again as clean air laws in the UK allowed lichen to recover.

The term “industrial melanism” is used to describe animals that adapt their colors to industrial pollution like soot, and was an early example used to support Charles Darwin’s theory of evolution.

The peppered moth was originally pale in color, but eventually evolved into a darker form when the air pollution of the Industrial Revolution caused tree bark to darken with soot and lichen was killed off.

As lichen recovered and levels of soot in the atmosphere went down, the species turned pale again. This is a good thing for the moths, as scientists on Friday published findings that indicate the paler moth has an evolutionary advantage over the darker one.

The study, published in the journal Communications Biology, looked at the survival rates of both moths based on how well birds are able to see them.

The University of Exeter scientists used digital image analysis and field experiments in woodlands to compare how birds see the different moths.

A peppered moth that adapted to soot and air pollution by turning black. (Olaf Leillinger via Wikipedia)

“Through a bird’s eyes, the pale peppered moths more closely match lichen-covered bark, whereas darker individuals more closely match plain bark,” said researcher Olivia Walton.

“Crucially, this translates into a strong survival advantage; the lighter moths are much less likely to be seen by wild birds when on lichen-covered backgrounds, in comparison to dark moths.”

Birds see a wider range of colors than humans, and most are able to perceive ultraviolet light.

The scientists also did experiments using fake moths which they baited with food, then observed how often they were eaten by birds.

They found that the lighter model had a 21 percent higher chance of not being eaten by birds like sparrows, robins, tits and blackbirds.


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