A mosquito species linked to urban environments has a history that predates the advent of the London Underground by centuries. Culex pipiens f. molestus, known colloquially as the London Underground mosquito, became notorious post-World War II as Londoners sought refuge in tube stations during the Blitz.
This mosquito variant is closely related to the bird-biting Culex pipiens f. pipiens. Until recently, scientists believed that Culex pipiens f. molestus evolved in urban areas within the last few hundred years. However, a groundbreaking study involving the DNA analysis of 790 mosquitoes from 44 countries reveals a much older origin. Researchers have traced its evolutionary roots to the Middle East thousands of years ago.
The study presents three compelling pieces of evidence for this theory. Firstly, genetic comparisons show that molestus mosquitoes are genetically closer to Mediterranean populations of pipiens than to their northern European counterparts, indicating a shared lineage. Secondly, molestus mosquitoes in the eastern Mediterranean display greater genetic variability than those found in northern European underground habitats, suggesting a longer presence in that region. Lastly, the absence of the pipiens form in the Middle East supports the idea that the ancestors of molestus mosquitoes evolved independently to adapt to human hosts without interbreeding with bird-biting relatives.
The findings point to an ancient lineage, with estimates suggesting that molestus mosquitoes may have diverged from their ancestors between 1,000 and 10,000 years ago—aligning with the onset of agricultural practices in the Middle East. This pre-adaptation for urban life suggests that molestus mosquitoes were already well-equipped for city habitats well before they colonized urban spaces.
As cities become more crowded, the potential for hybridization between molestus and pipiens mosquitoes could increase, raising public health concerns. The emergence of hybrids may lead to intermediate behaviors and a heightened ability to transmit diseases such as West Nile virus from birds to humans.
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