Scientists track genetic race between humans and mosquitoes

Los Angeles: Mosquitoes are likely to evolve resistance against insecticides or unfavourable climate conditions typica l in their local environment, according to a new study. The study suggests that understanding the genomes of these populations could help inform agencies which pesticides are likely to be most effective against them. Scientists studying mosquitoes in various types of environments in the US and in Russia found that between 5 and 20 per cent of a mosquito population’s genome is subject to evolutionary pressures at any given time – creating a strong signature of local adaptation to environment and humans.

This means that individual populations are likely to have evolved resistance to whatever local selection pressures are typical in their area – and that understanding the genomes of those populations could one day help inform agencies about which pesticides are likely to be most effective against them. “Mosquitoes adapt to heat, lifestyle, pesticides and so on – and we see traces of that in their genome,” said co-author Sergey Nuzhdin, professor at University of Southern California(USC) Dornsife College of Letters, Arts and Sciences. For the study, scientists in the US and Russia teamed up to sequence the genomes of various populations of mosquitoes – looking at urban and suburban mosquitoes in their countries and also at two different but related species – Culex pipiens and Culex torrentium.

They then tracked which genes were evolving the fastest by noting which were preserved most accurately in each genome. Genes are subject to various copying errors. If there are a lot of variations throughout a population of a specific gene, then it probably isn’t crucial to their survival. If, however, all members of a population have a near perfect copy of a given gene, then there is a good chance that natural selection is acting on it.  Based on which genes are being driven by evolution, the researchers found the widest variation between geographically separated populations than they did between populations in different types of environments.

That is, a suburban mosquito in US has more in common with an urban mosquito than it does with a suburban mosquito in Russia. “In addition to the insights into the contemporary evolution of mosquitoes, the methods we used in this study can be applied to compare genes under natural selection across populations of any species, including humans,” said lead author Hosseinali Asgharian, student at USC Dornsife. The scientists hope that the knowledge will help inform strategies to control mosquito populations. Culex pipiens, for example, can carry West Nile Virus, a disease that has no medications to treat it, nor vaccines to prevent it.

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