Scorching dragonfly summers

 Scorching dragonfly summers: species with darker wings have adapted to endure high temperatures while also enhancing their ability to attract mates.

In some dragonfly species, males display dark markings on their wings to attract mates, but this comes at a price—those dark spots absorb more heat, leading to thermal stress. Researchers have now discovered that dragonflies with darker wing coloration have evolved to tolerate higher temperatures, potentially shaping how populations will cope with future climate change.

Temperature is crucial in determining where species can thrive and their vulnerability to warming climates. While heat tolerance has been extensively studied in terms of survival, less is known about its impact on reproduction, which is closely tied to extinction risk.

In a new study published in Frontiers in Ethology, U.S. researchers explored whether males of dragonfly species that produce sexual signals through dark wing coloration are more heat-resistant. "We found that dragonflies with dark breeding coloration have also evolved the ability to tolerate higher temperatures," explained Dr. Noah Leith from the University of Pittsburgh. This finding opens a new research avenue into the link between thermal traits and sexual signals.

Dark wing markings, which help dragonflies attract mates and compete for reproductive territories, increase body temperature by absorbing heat. This can lead to physiological stress or even force males to abandon mating grounds. Despite these risks, animals often prioritize reproduction, even in potentially lethal heat conditions, Leith noted.

The team studied the wing coloration of 14 tropical and five temperate dragonfly species. They found that those with dark, heat-absorbing wings were better able to handle higher temperatures before reaching critical thermal thresholds. "This ability to withstand heat is key to understanding how dragonflies may respond to future climate shifts," said Leith.

Dark wing patches can raise body temperature by 1°C to 2°C, closely aligning with the increased heat tolerance of species with these markings. The arch-tipped glider (Tauriphila argo), a tropical species with dark patches near its core, showed the highest heat tolerance. This evolutionary link was particularly pronounced in tropical species.

Past research has shown that as global temperatures rise, some dragonflies are evolving to have less dark coloration. However, this new study suggests that even if species lose their dark spots, they may still adapt to climate change because they've already evolved to withstand heat.

This is one of the first studies to examine how thermal tolerance evolves alongside reproductive traits. Leith emphasized that dark sexual coloration, which causes heat absorption, is common across many animal species, from reptiles to lions and fruit flies. As climate change accelerates, predicting which species are at risk of extinction is critical. "We need to understand how reproductive traits interact with survival traits to predict how animals will cope with extreme environments," said Leith.

Although the study focused on 19 dragonfly species, the researchers noted that thousands exist. Future research should explore whether similar evolutionary patterns occur in other dragonfly species and animals. "It would be fascinating to test if heat tolerance evolves alongside sexual traits across the broader spectrum of life," Leith concluded.