Mosquitoes are ‘cold-blooded’ animals that require certain temperature ranges to survive, develop, and reproduce. With climate change spurring a warmer planet, some researchers have been predicting that rising temperatures can drive the insects to cooler regions, contracting their populations near the tropics.1
“But whenever we share this, the first question is always, well, what if mosquitoes adapt?” said Lisa Couper, a disease ecologist in Justin Remais’s lab at the University of California, Berkeley.
Now, Couper and her team have found that mosquitoes have the potential to evolve and adapt to higher temperatures on pace with global warming.2 Their results, published in Proceedings of the National Academy of Sciences, highlight that accounting for mosquito adaptation is crucial to predicting their distribution in a warming planet. These predictions are important for researchers to understand how warming reshapes the global map of mosquito-borne diseases like dengue, malaria, and Zika fever.3
To collect mosquitoes for her experiments, Lisa Couper sampled tree holes in Solano County, California.
Lisa Couper
“This is a good piece of work,” said Deepa Agashe, an evolutionary biologist at the National Center for Biological Sciences, who was not involved with the study. “They show quite nicely and convincingly that, if you're starting off with a diverse mosquito population, they should be able to adapt pretty fast to the changing climate.”
For their experiments, Couper and her team used the mosquito Aedes sierrensis, a common pest in western North America that spreads heartworms to dogs. They collected mosquito larvae from various tree holes in California and let the insects reproduce for two generations in the lab.
For the third generation, they turned up the heat. While they exposed some larvae to 30°C, the maximum temperature they can survive over a prolonged period, others were maintained at their natural temperature of 22°C. Mosquitoes in the prolonged heat-exposed group had significantly lower survival rates compared to controls.
Couper and her team wondered how prolonged heat exposure affected acute heat tolerance in the mosquitoes that survived to adulthood. They sealed each insect in a vial, immersed it in a gradually warming water bath, and observed how long it took for motor function to wane. Compared to control mosquitoes, those exposed to high temperatures as larvae exhibited motor deficits more quickly, suggesting a lower heat tolerance.
The researchers reared Aedes sierrensis adults in cages in the lab.
Lisa Couper
“This was initially counterintuitive,” said Couper, who thought that larvae exposed to heat would fare better in hot conditions later in life.
Researchers have previously shown that warmer developmental temperatures can result in smaller body sizes in animals.4 Consistent with this, mosquitoes that faced higher temperatures as larvae were significantly smaller than those from the control group. “Smaller body sizes are often found to have lower short-term heat tolerance just because there's kind of a lower resource level to start with,” noted Couper. “So, it’s not that counterintuitive at all.”
The researchers then investigated the genetic changes underlying prolonged and acute heat tolerance. They sequenced the DNA from all the mosquitoes that survived to adulthood and compared this with the genome of a control mosquito. They identified more than 500,000 single nucleotide mutations, including hundreds in genes associated with thermal tolerance.
These mutations were highly clustered in certain regions of the genome, indicating the presence of structural changes in those areas. Structural changes, including chromosome inversions, where a piece of a chromosome breaks off and reattaches in the reverse orientation, are linked to mosquito climate adaptation.5 In line with this, Couper and her team identified more than 80 chromosomal inversions in the mutation-rich genomic region.
For their experiments, the researchers reared and maintained pupal (left) and adult (right) Aedes sierrensis in the lab.
Lisa Couper
Finally, the researchers estimated the maximum rate at which thermal tolerance could evolve and compared it to the projected rates of warming during spring, the larval activity period. They found that the estimated adaptation rates exceeded the rates of warming.
The results suggest that warmer regions may not see a decline in mosquito populations with rising temperatures, said Couper. “[This] really speaks to the fact that we need to keep the foot on the gas in terms of mosquito borne disease prevention.”
“This is a really worrisome thing for things like vectors,” agreed Agashe. On the other hand, she added, “If this is true for several other insect species, then maybe there's hope that there will not be devastating losses of insects in general.” However, more work is needed before researchers know whether all insects can adapt to climate change, she cautioned.
For instance, experiments carried out over a single generation may not accurately predict the long-term consequences of environmental changes. Agashe added that follow up studies could also investigate how additional factors, such as interactions with other species in their natural contexts, impose selection pressures that may alter adaptive outcomes.
Couper agreed. “We're finding this evolutionary potential, but exactly what will happen in nature will depend on the context.”
- Ryan SJ, et al. Global expansion and redistribution of Aedes-borne virus transmission risk with climate change. PLoS Negl Trop Dis. 2019;13(3):e0007213.
- Couper LI, et al. Evolutionary adaptation under climate change: Aedes sp. demonstrates potential to adapt to warming. Proc Nat Acad Sci USA. 2025;122(2):e2418199122.
- Ryan SJ, et al. Global expansion and redistribution of Aedes-borne virus transmission risk with climate change. PLoS Negl Trop Dis. 2019;13(3):e0007213.
- Peralta-Maraver I, Rezende EL. Heat tolerance in ectotherms scales predictably with body size. Nat Clim Change. 2020;11(1):58-63.
- Small ST, et al. Standing genetic variation and chromosome differences drove rapid ecotype formation in a major malaria mosquito. Proc Nat Acad Sci USA. 2023;120(11):e2219835120.
