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‘Straightjacket’ may spell disaster for overheated flies

MONASH U. (AUS) — Many fruit fly species may face extinction in the near future due to an evolutionary “straitjacket” that makes it difficult for them to adapt to rising global temperatures.

Current projections predict a 3ºC increase in mean annual temperature in the next century and even greater increases in extremes, says Vanessa Kellermann from Monash University’s School of Biological Sciences.
“Given our findings, these expected increases pose a major threat to biodiversity in the near future. Particularly as Drosophila or fruit fly findings are often more broadly applicable,” adds Kellermann.

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By examining nearly 100 species of fruit fly from around the world, the researchers show that species have evolved to the temperature extremes and humidity of their environments. However, they have had very little flexibility to change their levels of heat resistance and seem unable to adapt to increased temperatures in the future.

High heat resistance is a feature of only some branches of the phylogeny—the tree that shows how species are related through evolutionof Drosophila. Other branches had very limited ability to change their levels of heat resistance; even when flies native to cooler areas grew up in a warm environment, their heat tolerance was not significantly altered.

“The problem is that only a handful of species have adapted to hot environments while most species have not and it seems very difficult to switch once you are stuck on a phylogenetic branch,” Kellermann says.

The researchers looked at species’ prospects for dealing with projected temperature increases in the near future. They report their findings in the Proceedings of the National Academy of Sciences,

“If a species can only withstand temperatures of 36ºC and the maximum temperature of the environment is already 36ºC, an increase of even 1ºC would already put this species over the edge towards extinction,” Kellermann says.

Using this method, the researchers identified at-risk species and found that most tropical and mid-latitude species fell into this category.

“Without rapid adaptation, which now seems very unlikely, a lot of species may fall over under even a mild increase in temperature.”

Researchers from the University of Melbourne contributed to the study.

Source: Monash University

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