November 15, 2018, by Tim Radford
Warning in Guiana of dengue fever: Mosquitoes spread the virus. Image: By Cayambe via Wikimedia Commons
In the long term, some creatures will adapt to climate change and evolve. Mosquito evolution could bring new species – and new diseases.
LONDON, 15 November, 2018 – The hot breath of climate change could blow in new health hazards – if the past is a reliable guide. A shift in mosquito evolution could be triggered by ever greater levels of carbon dioxide in the atmosphere, fossil evidence matched with climate simulations suggests.
And in a new climate, and with new opportunities, there could follow new diseases, according to British researchers.
Mosquitoes already carry infections such as malaria, yellow fever, Zika virus, West Nile virus and dengue fever: diseases that kill millions each year. And mosquitoes are more than usually sensitive to CO2, which they exploit to detect potential sources of blood from the mammals on which they prey.
Researchers have repeatedly worried about what warming temperatures and changing climate could do for the mosquito-borne return of malaria to those cooler climates normally considered safe, and about the potential spread of tsetse fly as its normal habitat becomes too hot.
But any new emergent diseases from the mosquito remain academic: the scientists foresee evolutionary opportunities, likely to emerge over very long timespans.
“It’s only the female mosquitoes that take a blood meal, and they use the CO2 that mammals and other vertebrates exhale as a very general cue to locate their hosts”
Researchers report in the journal Communications Biology that they looked carefully at what they could establish about mosquito evolution, composed a “supertree” of the disease-bearing insect and its relatives, and mapped it against what they knew of past climate change.
There are mosquito fossils – though not very many – but these served as a kind of check on the evidence from the mathematical models of evolution that emerged.
As carbon dioxide levels rise, with ever greater combustion of fossil fuels to drive global warming, it could paradoxically be more difficult for mosquitoes to prey on their usual hosts. Environmental change provides opportunities for new evolutionary niches – and perhaps mosquitoes could find new hosts, and new infectious diseases could evolve?
“It’s only the female mosquitoes that take a blood meal, and they use the CO2 that mammals and other vertebrates exhale as a very general cue to locate their hosts.
“One line of thinking is that as ambient levels of atmospheric CO2 rose, mosquitoes may have found it increasingly difficult to distinguish between the CO2 from their hosts and those background levels,” said Matthew Wills, of the University of Bath, one of the authors.
“Vision, body heat and other smells might then have become more important in locating their blood meals, but many of these cues tend to be more specific to particular hosts. As a general rule, we know that a strong host specificity can be an important driver of speciation in parasites, and the same may be true in mosquitoes.”
And Katie Davis, of the University of York, said: “We found that the increase in the diversity of mammals led directly to a rise in the number of mosquito species, and also that there is a relationship between CO2 levels and the number of mammal species, but there are still missing pieces of this puzzle, so we can still only speculate at this stage.”
But, she said, the research showed that mosquitoes could adapt to climate change and evolve. “With increased speciation, however, comes the added risk of disease increase and the return of certain diseases that had eradicated them or never experienced them before.” – Climate News Network
Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.