UC Santa Cruz

Many aspects of mosquito biology are highly sensitive to variation in temperature, which has led to predictions that climate change will alter the transmission of many vector-borne pathogens. However, it is unknown how mosquitoes will evolve in response to changing climates. We utilized common garden experiments and novel time-compressed climate change scenarios to examine standing geographic variation, species variation, and evolutionary change in the temperature dependence of four life history traits of mosquitoes (larval and adult survival, development rate, and biting rate).

First, we quantified spatial variation in life history traits for four populations of Culex pipiens mosquitoes, a primary vector of West Nile Virus in North America, to examine the extent to which mosquitoes might be adapted to local thermal environments. We found substantial variation in life history traits among mosquito populations that was uncorrelated with local thermal conditions. This variation will shape the response of mosquito species to changing climates and will make the impact of climate change on vector-borne disease more variable and less predictable than previously thought.

Second, we quantified variation in life history traits and vectorial capacity for the two dominant mosquito vectors of Zika, dengue, chikungunya, and yellow fever viruses, Aedes aegypti and Aedes albopictus. Differences in life history traits were mixed with Ae. albopictus having faster development, higher larval survival, and more frequent feeding, whereas Ae. aegypti had higher adult survival. Ae. aegypti was a slightly more efficient vector of all four viruses, and vectorial capacity was highest for yellow fever virus followed by Zika, Chikungunya and dengue.

Lastly, we reared Ae. aegypti under three rates of temperature increase (+2°C, +4°C, and +5°C) and three control conditions (a 2°C decrease, and two temperature profiles with no net change) for one year to examine the potential evolutionary response to climate change. Although there was significant among-treatment variation in four life history traits between the starting population and the six climate treatments, these differences were uncorrelated with the temperature regime the mosquitoes experienced, suggesting that the mosquitoes were adapting more to the increased variance in temperatures in the experiment than the differences in mean temperature.