Iowa State scientist helps rewrite mosquito evolution story

An Iowa State University scientist is part of an international team of researchers that has upended one of the most famous examples of urban evolution: the human-biting mosquito.

The discovery, published in “Science,” reveals that the mosquito form known for transmitting West Nile virus to humans didn’t evolve in modern European cities as long believed, but likely originated 1,000 — 10,000 years ago, likely in ancient Egypt.

Dr. Ryan Smith, associate professor in the department of plant pathology, entomology, and microbiology at Iowa State, is part of the global “PipPop Consortium” that conducted the groundbreaking study. His lab contributed key genetic analyses and mosquito samples that helped trace the evolutionary history of Culex pipiens form molestus, a mosquito adapted to living in close quarters with humans.

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“This species has been an evolutionary mystery for decades,” said Smith, who leads ISU’s Vector Biology Research Group. “The prevailing theory was that these mosquitoes evolved recently in underground spaces like subway tunnels in London. What this new research shows is that human-biting behavior evolved much earlier, likely in agricultural societies thousands of years ago.”

The study, led by Princeton University and involving over 150 institutions worldwide, analyzed DNA from more than 12,000 Culex pipiens mosquitoes. The results reveal that the so-called “molestus” form, famous for biting humans and thriving in urban environments, diverged long before the rise of modern cities.

Smith said the work has important implications for public health and disease ecology, particularly regarding West Nile virus, for which mosquitoes of the Culex pipiens complex transmit virus between birds and humans.

“Understanding the genetic relationships between the bird-biting and human-biting forms helps us predict when and where hybridization might occur,” said Smith. “That’s critical, because it’s these hybrids, mosquitoes that bite both birds and humans, that can spread West Nile virus most efficiently.”

Current research suggests that hybridization is less common than previously thought but tends to occur in large urban areas, potentially increasing disease risk where people and wildlife overlap.

The Iowa State team, including Chris Lee, a current lab assistant, and Dr. Ryan Tokarz, a former post-doc in the lab, contributed mosquito samples collected through ongoing mosquito surveillance efforts in Iowa. Their participation helped expand the genetic dataset that made this global comparative study possible.

“It’s exciting to see our local work connect to such a global effort,” said Smith. “This collaboration shows how science thrives when researchers across continents share data and expertise to solve complex biological puzzles.”

The research opens new avenues for studying how urbanization shapes mosquito genetics and disease transmission patterns.