Liverpool team sheds light on the peppered moth’s dark past

Peppered Moth

A mating pair of the black (male) and typical (female) forms of the peppered moth

A team of scientists from the Institute of Integrative Biology has discovered that the mystery of the rapid spread of the dark form of the peppered moth in the 19th century was the result of a single genetic mutation that spread rapidly through the population through natural selection.

For decades the peppered moth served as a text book example of rapid evolutionary change in response to alternation of the natural environment by human activity. The typical form of the peppered moth has light-coloured wings.

However, during the industrial revolution the dark form of the peppered moth displaced the lighter form to avoid predators by blending in with the sooty bark on the trees. As air pollution reduced in the 1970s, the dark form began to decline and the lighter form resurged.

Dr Ilik Saccheri and his team used molecular genetics to show that one mutation from a single ancestor causes increased dark pigment, called melanism, in the typically lighter coloured moth. The team examined black moths from 80 sites across Britain and identified the region of chromosome – chromosome 17 – as being responsible for the colour change. Interestingly, the same region is one in which mutations produce different wing colour patterns in distantly related butterflies.

Dr Ilik said: “I think we have strong evidence that industrial melanism in the UK was seeded by a single recent mutation, however, more research is needed to identify the exact DNA changes which led to the changes in colour.”

The results are published online in Science.

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