As mosquitoes dominate warm climates and play a larger role in human health issues, understanding how they spread becomes increasingly important. How do mosquitoes, particularly ones in the prolific Aedes genus (which includes Aedes aegypti and Aedes albopictus, the species that transmit Zika virus), utilize the landscape to disperse to new locations?
New research on the invasive mosquito Aedes japonicus japonicus has shown that the natural landscape isn’t the only open pathway for mosquitoes to spread. Using a high-resolution landscape genetic analysis of 461 mosquito specimens collected across Virginia, Egizi et al., in their recent paper in Molecular Ecology, determined how populations spread from their original introduction in the north-eastern U.S. in the 1990’s.
They found that Ae. j. japonicus most likely dispersed using human corridors, specifically the I-95 interstate corridor in the eastern part of the state that connects Virginia to northern populations in Pennsylvania. The I-95 corridor can also be linked to two other factors associated with mosquito presence: the presence of military bases, which have high human turnover, and the presence of tires and tire shops, where the mosquitoes are likely to leave larvae.
Although stream corridors were a likely possibility for mosquito dispersal, there was no evidence that Ae. j. japonicus spread autonomously over long-distance via such natural pathways. Even over shorter distances, human-mediated dispersal was more common than autonomous dispersal. In short, human corridors played a critical role in allowing the species to move beyond its own limited dispersal abilities. Apparently, where the cars go, the mosquitoes go as well, making humans mostly responsible for this particular invasion.
Egizi, A., J. Kiser, C. Abadam, and D. M. Fonseca. 2016. The hitchhiker’s guide to becoming invasive: exotic mosquitoes spread across a US state by human transport not autonomous flight. Molecular Ecology 25(13): 3033-3047.