A study in the Proceedings of the National Academy of Sciences led by Michael Moore at Washington University in St. Louis reveals that male dragonflies have consistently evolved less breeding coloring in areas with warmer climates.
“Our study shows that the wing pigmentation of male dragonflies evolves so steadily in response to climate that it is among the most predictable evolutionary responses ever observed for a mating-related trait,” said Moore, who is postdoctoral fellow at the Living Earth Collaborative. .
“This work reveals that traits related to mating can be just as important to how organisms adapt to their climate as traits related to survival,” he said.
Many dragonflies have spots of dark black pigmentation on their wings which they use to woo potential mates and intimidate rivals.
“Beyond its reproductive function, having a lot of dark pigmentation on the wings can heat dragonflies up to 2 degrees Celsius, a pretty big change!” Moore said, noting that this would roughly equate to a 3.5 degree Fahrenheit change. “While this pigmentation can help dragonflies find mates, additional heating could also cause them to overheat in already hot places.”
The researchers wanted to know if this additional heating could force dragonflies to develop different amounts of wing pigmentation in different climates.
For this study, scientists created a database of 319 dragonfly species using field guides and citizen scientist observations. They examined the wing ornamentation shown in the photographs submitted to iNaturalist and gathered information on climatic variables in the locations where the dragonflies were observed. The researchers also directly measured the amount of wing pigmentation on individual dragonflies from nearly 3,000 iNaturalist observations in a target group of 10 selected species. For dragonflies of each of these 10 species, scientists assessed how populations differed in the hot and cold parts of their geographic range.
Whether they’re comparing species in warmer or cooler geographies, or comparing populations of the same species living in warmer areas versus cooler areas, the researchers found the same: male dragonflies almost always responded to warmer temperatures by developing less wing pigmentation.
Sorting the observations in another way, the researchers determined that male dragonflies spotted in warmer years tended to have less wing pigmentation than male dragonflies of the same species in cooler years (the database included observations recorded during the period 2005-19).
âSince our planet is expected to continue to warm, our results suggest that male dragonflies may eventually need to adapt to global climate change by changing wing coloring less,â Moore said.
The study includes projections, based on global warming scenarios, which indicate that it will be beneficial for male wing pigmentation to decrease further as the Earth warms over the next 50 years.
But the changes do not happen in the same way for both sexes.
âUnlike males, female dragonflies show no major changes in the way their wing coloring changes with the current climate. We don’t yet know why males and females are so different, but it shows that we shouldn’t. not assume that genders will adapt to climate change the same way, âMoore said.
Dragonflies have different amounts of pigment on their wings which help males and females of the same species identify with each other. One of the interesting implications of this research is that if the wing pigmentation of males changes in response to rapid changes in climate and the pigmentation of females changes in response to something else, females may no longer recognize males on their own. species.
This could cause them to mate with males of the wrong species.
âRapid changes in mating-related traits could hamper a species’ ability to identify the right mate,â Moore said. âEven though our research suggests that these pigmentation changes seem likely to occur as the world warms, the consequences are something we don’t know much about yet. “
This work was done in collaboration with: Kim Medley, Director of the University of Washington Environmental Field Station, Tyson Research Center; Kasey Fowler-Finn, associate professor of biology at the University of Saint Louis; and Washington University undergraduates Kaitlyn Hersch, Chanont Sricharoen, Sarah Lee, Caitlin Reice, Paul Rice, and Sophie Kronick.