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Genetic study shows London's underground mosquitoes evolved from Egyptian species

A large international team of researchers has discovered that the mosquitoes that live in London's underground subway evolved from a Middle Eastern species over thousands of years. In their posted on the bioRxiv preprint server, the group describes how they studied the DNA of hundreds of specimens collected from multiple countries around the world, and what they learned by doing so.

During World War II, when German bombers appeared over the skies of London, many of the people living there made their way down into the tunnels used for the city's metro system, hoping to stay alive. Over time, tales of life in the tunnels began to emerge during the war. One such tale revolved around bothersome mosquitoes, making life even more miserable for those seeking shelter.

For many years, it was believed that the mosquitos had evolved to live in the tunnels after they had been built. Over the years, that theory was quashed as the same species of mosquito was found in many cities across the world, living in different environments.

Despite such findings, the mosquito came to be informally known as the London Underground mosquito. In this new effort, the research team set out to learn more about the evolutionary history of the mosquito, which is formally known as Culex pipiens f. molestus.

By collecting hundreds of samples from other countries, including species that are closely related, such as Culex pipiens f. pipiens, and then sequencing their DNA, the researchers were able to piece together some of their evolutionary history going back thousands of years. In so doing, the research team found evidence strongly suggesting the species first arose in the Middle East, most likely in Egypt.

The researchers found three main arguments for their findings. The first is that the molestus species was closer to pipiens originating in the Mediterranean basin than others in Europe. Second, molestus in the Mediterranean region today is more genetically variable than molestus found in underground places today, such as London's tube tunnels. And third, pipiens do not exist today in the Middle East, suggesting that ancestors of the molestus could have colonized parts of Europe without intermingling with pipiens.

The research team concludes by suggesting that molestus has been in Europe much longer than thought, perhaps going back to the dawn of agriculture.