Bad news – mosquitoes prefer heat and actually thrive in the warming climate

Recent research from Washington University in St. Louis sheds new light on the varying heat tolerances among mosquito populations, a discovery with significant implications for global health.

In a world increasingly threatened by vector-borne diseases, understanding mosquito behavior in response to rising temperatures is more crucial than ever.

Traditionally, models predicting vector-borne disease risks have operated under the assumption that all mosquito populations share similar heat tolerances.

This new study, however, challenges that notion, suggesting that some mosquitoes are better equipped to withstand heat waves than others.

Such findings indicate that current models might be underestimating the potential for disease spread in warmer climates.

Studying mosquito heat tolerance

This research was led by senior scientist Katie M. Westby at Tyson Research Center.

Westby and her team focused on the critical thermal maximum (CTmax) — the highest temperature an organism can tolerate — of the Aedes albopictus, or tiger mosquito. This species is a known carrier of diseases like West Nile, chikungunya, and dengue.

“We found significant differences across populations for both adults and larvae, and these differences were more pronounced for adults,” Westby said.

This study is pivotal, as it highlights significant variations in mosquito heat tolerance across different populations of this globally invasive species.

Westby’s team analyzed mosquitoes from eight distinct populations across four U.S. climate zones, ranging from New Orleans, Louisiana to Allegheny County, Pennsylvania.

By raising larvae from these various regions to adulthood under controlled laboratory conditions, the researchers were able to conduct thorough tests on their thermal limits.

What the research team learned

Surprisingly, the study found that adult mosquitoes generally had lower heat limits compared to their larvae. This disparity is likely due to the differing environments experienced by aquatic larvae and terrestrial adults.

“Larvae had significantly higher thermal limits than adults, and this likely results from different selection pressures for terrestrial adults and aquatic larvae,” said Benjamin Orlinick, first author of the paper and a former undergraduate research fellow at Tyson Research Center.

“It appears that adult Ae. albopictus are experiencing temperatures closer to their CTmax than larvae, possibly explaining why there are more differences among adult populations.”

Notably, adult mosquitoes tend to endure temperatures closer to their thermal heat maximum, accounting for the greater variance observed among adult populations.

One key finding of the research is the correlation between higher precipitation levels and increased heat tolerance in mosquitoes.

This suggests that in wetter climates, mosquitoes may better endure higher temperatures, possibly because increased humidity reduces their risk of dehydration.

“The overall trend is for increased heat tolerance with increasing precipitation,” Westby said. “It could be that wetter climates allow mosquitoes to endure hotter temperatures due to decreases in desiccation, as humidity and temperature are known to interact and influence mosquito survival.”

Mosquitoes, heat, and climate change

The study also highlights the importance of understanding how mosquitoes adapt to local climates and the potential for these insects to adjust to rapidly changing global temperatures.

According to Westby, genetic variation in heat tolerance is crucial for adaptation to rising temperatures.

“Standing genetic variation in heat tolerance is necessary for organisms to adapt to higher temperatures,” Westby said. “That’s why it was important for us to experimentally determine if this mosquito exhibits variation before we can begin to test how, or if, it will adapt to a warmer world.”

Looking forward, the team at Washington University plans to explore further into the limits of mosquito behavior, particularly how high temperatures impact their blood-feeding habits and potential adaptations to warmer conditions.

This research is vital for grasping the full impact of climate change on disease transmission, as real-world conditions often vary significantly from laboratory settings.

In summary, this disturbing study challenges existing models of disease risk while opening new avenues for understanding and mitigating the impact of climate change on public health.

The full study was published in the journal Frontiers in Ecology and Evolution.

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