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Climate change can steal its dark spots from male dragonfly wings

Many dragonflies fly through the air with translucent wings painted in a series of dark spots and bands. But, at least for men, those simple decorations could soon go out of style as a result of climate change.

The patches of the dark wings of males are smaller in dragonflies of a certain species that live in warmer climates than in colder regions, the researchers reported in the Proceedings of the National Academy of Sciences on July 13th. That finding suggests that dragonfly populations over time may experience a decrease in their spots as temperatures increase. Evolutionary change can not only dampen the appearance of male insects, but also their married life.

Understanding how organisms have adapted to warmer climates over the years is key to understanding how they can adapt to future weather conditions, says Michael Moore, an evolutionary ecologist at the University of Washington in St. Louis. Louis.

The strong pigmentation of the wings can help dragonflies stay warm in colder regions, but can be dangerous when it gets hotter. Dark spots absorb sunlight and can heat the wings up to 2 degrees Celsius, which can cause tissue damage and interfere with flight, Moore says. Throwing or lowering spots is a way to beat heat and can produce a color-changing response to climate change between owls similar to owls (SN: 7/11/14) and hares (SN: 26/1/16). . But adaptation could also confuse communication with peers.

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Male dragonflies use wing spots to attract mates and intimidate rivals, and females rely on these spots to recognize potential mates of the same species. The marks differ greatly between species, ranging from small specks near the base of the wing to extensive bands or panels spread throughout the wing.

Most organisms, says Moore, "not only need to survive in order to persist and perpetuate their species within the habitats in which they live, they also need to be able to reproduce."

He and his colleagues compiled a database of dragonfly wing patterns from a combination of field guides and many thousands of observations from citizen scientists across North America on the application of iNaturalist nature identification. The researchers found that male dragonflies of species found in warmer regions were less likely to evolve wing spots than their cold-weather counterparts.

To explore how quickly these color patterns could evolve, Moore and his team selected 10 species and compared wing spots in warmer, colder regions of a species range. In this way, the team was able to see if spot patterns within an individual species can adapt to local climatic conditions, which would be a faster evolutionary response than between different species. When it was warmer, males from seven of the 10 species evolved to have wings with fewer and fewer dark spots, the team discovered. The changes appear to have occurred even on a scale of decades: male dragonflies in the warmer years from 2005 to 2019 presented the smallest wing spots on average.

That change could have alarming consequences for insects. “It’s not hard to imagine that very rapid declines in wing coloration could cause females to not recognize males of their own species,” Moore says.

Most research to date on insect color and climate change has focused only on heat tolerance, says Lauren Buckley, an ecologist at the University of Washington in Seattle who did not participate in the study. "This research reveals the value of examining multiple competitive features of traits." Buckley says it’s important to see how changes in points affect all the work they do.

Dragonflies often move in and out of areas near water that may have very different temperatures, so future research could “better explain how dragonflies experience their environments,” she says.

Unlike males, the wing spots on females do not appear to respond to temperature, which was surprising, Moore says. It is possible that more regular use by females of shaded habitats outweighs the effect of higher temperatures.

That finding “indicates that we shouldn’t necessarily assume that males and females are going to adapt to climates in exactly the same way,” Moore says. "That has really big implications for how we think about modeling and predicting responses to future climates."

For now, Moore says, he wants to get an estimate of how much changes in wing points can disrupt the dragonfly dating game.

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