Peppered moths in England changed their camouflage during the Industrial Revolution, as buildings and trees around the city became darkened by soot and other pollution from early factories. New research suggests this change was driven by the same genes responsible for the brightly-colored wings of tropical species.
Cortex is a gene now suspected of driving colors on the wings of butterflies and moths. This includes changes seen in the peppered moth in the 19th century. This segment of genetic code is known to assist in cell division, and researchers are still uncertain how it alters wing color.
"What's exciting is that it turns out to be the same gene in both cases. For the moths, the dark coloration developed because they were trying to hide, but the butterflies use bright colors to advertise their toxicity to predators. It raises the question that given the diversity in butterflies and moths, and the hundreds of genes involved in making a wing, why is it this one every time?" Chris Jiggins of the University of Cambridge said.
Wings of these insects possess minuscule scales, layered in alternating rows.
Before the development of widespread mechanical manufacturing, peppered moths in England were salt-and-pepper-colored, camouflaging themselves against the lightly-colored trees. By 1819, air pollution started to kill lichen that lived on the trees, and also blackened the trees.
Researchers know of 17,000 different forms of butterflies, as well as 160,000 versions of moths. Every form of these Lepidoptera possess unique wing patterns. Until recently, biologists were uncertain how these features formed, despite more than 100 years of research.
The fact that peppered moths in England changed color during the Industrial Revolution, a process known as industrial melanism, has long been known. What is new is finding that this change was driven by the same genes that are responsible for the brilliant colors of tropical Heliconus butterflies, found throughout South America.
Investigators searching for the genes responsible for wing coloration were surprised to find the genetic code they were hoping to find was located in a different place than expected. Instead of being located in a stable place in the code, the target genes are located in transposons, which jump around segments of DNA.
Analysis of the underlying genetic cause of color changes in the peppered moth was profiled in the journal Nature.