Tiger mosquito,
spreading northwards, adapting.
Deadly time capsules.
Many mosquito species struggle to survive at low temperatures, preventing their spread into cooler climates and thus limiting the spread of diseases carried by the mosquitoes. Yet new research by Medley et al (2019) suggests that some mosquito species may be able to adapt part of their reproductive cycle to survive cold winters.
The Asian tiger mosquito is a vector for a number of pathogens, including Zika and dengue viruses. The species first arrived in the USA in Texas in 1985 and today the current range extends as far north New Jersey.
How has this tropical and sub-tropical species managed to survive the temperate conditions?
The secret lies with a process called diapause – a type of animal dormancy where development is delayed in response to unsuitable environmental conditions such as cold winters.
In the Asian tiger mosquito, the length of day or night (photoperiodism) can induce egg diapause – as the days get shorter with the approach of winter eggs become dormant and only start developing again once the days start to lengthen and temperatures are likely to be more suitable for the species.
In the new study the researchers found that northern diapause eggs survive northern winters a lot better than southern diapause eggs, but both northern and southern diapause eggs survive southern winters the same as each other. The research demonstrates the species adapting to colder conditions as it expands northwards over a period of around 30 years. Not only have northern populations adapted to northern climes by producing more eggs but those eggs are adapted to survive the northern winters better too.
Original research: https://doi.org/10.1111/1365-2664.13480