Ancient origin of an urban underground mosquito *Haba, Y., Aardema, M. L., Afonso, M. O., ..., Korlević, P., McAlister, E., Lawniczak, M.K.N., Schumer, M., Rose, N. H., *McBride, C. S. bioRxiv (2025)

Abstract

Urban mosquitoes that bite humans have evolved independently multiple times, but their origins and evolutionary drivers remain poorly understood. The London Underground mosquito represents one of the most extreme examples of urban adaptation, having colonized the tunnels of the London subway system where it feeds on humans rather than birds like its above-ground ancestors. Despite intensive study, the origins of this urban mosquito remain mysterious. Here, we present a comprehensive genomic analysis of Culex pipiens populations from around the world, including the London Underground, to uncover the evolutionary history of urban adaptation in this species complex. Using whole-genome sequencing of 1,024 mosquitoes from 121 populations across six continents, we reveal that the London Underground mosquito did not evolve recently from local above-ground populations, as previously hypothesized. Instead, our analyses support an ancient origin for this urban form, with genomic evidence suggesting that human-biting underground populations arose at least 1,000 years ago, long before the construction of the London Underground in the 1860s. We identify genomic regions that show parallel evolution across multiple urban mosquito populations, suggesting common genetic mechanisms underlying the transition from bird-biting to human-biting behavior. These findings reshape our understanding of urban mosquito evolution and highlight the potential for pre-adapted mosquito populations to exploit new urban environments as cities expand globally. Our results provide crucial insights into the genetic basis of host preference evolution and have important implications for vector control strategies in urban environments.

Origin and status of Culex pipiens mosquito ecotypes Haba, Y., McBride, L. Current Biology 32, R237-R246 (2022)

Abstract

The northern house mosquito Culex pipiens sensu stricto is one of the most important disease vector mosquitoes in temperate zones across the northern hemisphere, responsible for the emergence of West Nile Virus over the last two decades. It comprises two ecologically distinct forms — an aboveground form, pipiens, diapauses in winter and primarily bites birds, while a belowground form, molestus, thrives year-round in subways, basements and other human-made, belowground habitats, bites mammals, and can even lay eggs without a blood meal. The two forms hybridize in some but not all places, leading to a complex ecological mosaic that complicates predictions of vectorial capacity. Moreover, the origin of the belowground molestus is contentious, with iconic populations from the London Underground subway system being held up by evolutionary biologists as a preeminent example of rapid, in situ, urban adaptation and speciation. We review the recent and historical literature on the origin and ecology of this important mosquito and its enigmatic forms. A synthesis of genetic and ecological studies spanning 100+ years clarifies a striking latitudinal gradient — behaviorally divergent and reproductively isolated forms in northern Europe gradually break down into what appear to be well-mixed, intermediate populations in North Africa. Moreover, a continuous narrative thread dating back to the original description of form molestus in Egypt in 1775 refutes the popular idea that belowground mosquitoes in London evolved in situ from their aboveground counterparts. These enigmatic mosquitoes are more likely derived from populations in the Middle East, where human-biting and other adaptations to human environments may have evolved on the timescale of millennia rather than centuries. We outline several areas for future work and discuss the implications of these patterns for public health and for our understanding of urban adaptation in the Anthropocene.

A multivariate phylogenetic comparative method incorporating a flexible function between discrete and continuous traits Haba, Y., Kutsukake, N. Evolutionary Ecology 33, 751–768 (2019)

Abstract

One major challenge of using the phylogenetic comparative method (PCM) is the analysis of the evolution of interrelated continuous and discrete traits in a single multivariate statistical framework. In addition, more intricate parameters such as branch-specific directional selection have rarely been integrated into such multivariate PCM frameworks. Here, originally motivated to analyze the complex evolutionary trajectories of group size (continuous variable) and social systems (discrete variable) in African subterranean rodents, we develop a flexible approach using approximate Bayesian computation (ABC). Specifically, our multivariate ABC-PCM method allows the user to flexibly model an underlying latent evolutionary function between continuous and discrete traits. The ABC-PCM also simultaneously incorporates complex evolutionary parameters such as branch-specific selection. This study highlights the flexibility of ABC-PCMs in analyzing the evolution of phenotypic traits interrelated in a complex manner.