‘Jumping’ gene started the rise of peppered moths, study finds

The genetic mutation that caused a never-before-seen black type of moth emerge during the 18th and 19th century Industrial Revolution in the UK has finally been discovered, according to a new study published in the Wednesday, June 1 edition of the journal Nature.

The research, which was published alongside a second paper that detailed how this same genetic mutation enables tropical butterflies to use a variety of different color schemes, explained that an unusual “jumping gene” mutation was responsible for the rise of this dark variant of moth.

Furthermore, leaad investigator Ilik Saccheri of the University of Liverpool Institute of Integrative Biology and his colleagues were also able to find that the mutation first appeared around the year 1819, which “consistent with the historical record,” according to BBC News reports.

“This discovery fills a fundamental gap in the peppered moth story,” Dr. Saccheri explained in a statement. “The fact that this famous mutant is caused by a transposable element will hopefully attract more interest in the impact of mobile DNA on fitness and the generation of novel phenotypes.”

Despite the discovery, many questions still remain

The rise of black peppered moths, which the BBC called “an iconic evolutionary case study,” came during the early- to mid-19th century, with the first documented sighting taking place in Manchester, northern England, in 1848. However, experts have long suspected that they may have existed, undetected due to low population numbers, several years beforehand.

Now, Dr. Saccheri’s team has found that this evolutionary change, which was the result of soot darkening the walls and tree trunks of its habitat, took place nearly three decades before anyone first caught glimpse of one of these unusual moths. They used a statistical simulation to pinpoint how many generations would have been needed to achieve the levels of DNA sequence changes required to achieve the observed pattern of color variation.

“Our best estimate of 1819 shows that the mutation event occurred during the industrial revolution and that it took around 30 years for it to become common enough to be noticed,” study co-author Dr. Pascal Campagne, also from the University of Liverpool. His colleague, Dr. Arjen van’t Hof, added that the findings “provide an opportunity to further develop peppered moth industrial melanism as a tool for teaching evolutionary biology and the genetic basis of adaptation.”

Peppered moths, BBC News explained, were one of the earliest visible examples of evolutionary changes, as the creatures were first seen a decade before Darwin and Wallace originally outlined the concept of natural selection. The creatures are noctural, and these new color schemes made it much easier for the moths to sleep on trees or walls without being spotted by hungry birds.

To find out exactly what changes occurred in the species’ genes, Dr. Saccheri and his colleagues used traditional genetic mapping to find 87 different DNA differences between black moths and their white counterparts. Eventually, they found that the culprit was a transposon – a “jumping” piece of DNA that inserted itself into a gene called cortex. Strangely, however, cortex genes are not known to play a role in pigmentation, so exactly how this mutation caused black coloring in the moths remains a bit of a mystery.

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Image credit: Thinkstock

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