Study shows dragonfly color changes throughout the year

The color of dragonfly communities responds to seasonal variations in solar radiation. However, over the past 30 years this color structure has changed, probably due to climate change.

In a new study, researchers from Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany, found that the color of dragonfly communities responds to seasonal fluctuations in solar radiation. In spring and fall, dragonflies with darker shades of color are more likely to fly, while specimens that appear in summer tend to be lighter in color. The results of the study have now been published in the journal Natural communications.

Color adaptation allows predatory insects to regulate their body temperature. Dark colors absorb heat better than light colors. It is important to note that it is not individual animals that change color, explains Professor Christian Hof. He directs the new chair of global change ecology at JMU. “What changes and adapts to solar radiation, so to speak, is the average coloration of all dragonflies flying at any given time.”

Previous research has shown that in northern regions, darker-colored and larger dragonfly species tend to fly, because they are better able to retain heat. Lighter-colored species, on the other hand, are found in the sunny south, where their coloration protects the animals from overheating.

Color change during the year checked for the first time

The team led by Dr. Roberto Novella Fernandez and Professor Christian Hof began their work while at the chair of terrestrial ecology at the Technische Universität München (TUM) and completed it after joining JMU together.

For the study, they examined and analyzed scientific observation data of dragonfly communities from 1990 to 2020 in the UK. The researchers found that the average coloration of dragonflies changes seasonally.

“For the first time, we were able to prove that the average body brightness of dragonflies not only differs between warmer and colder regions, but also that lighter species tend to be found throughout the year. during months with stronger sunlight, that is, in summer, while darker specimens fly in spring and autumn,” explains Roberto Novella Fernandez, lead author of the study.

Christian Hof adds: “We also see in the evaluated data that this seasonal color variation has changed during climate change.” However, global warming mainly changes temperature and not solar radiation.

“Warming could even change the trend in an unfavorable direction for dragonflies, because they no longer fly in ideal solar radiation conditions. Understanding this in more detail is one of our next goals,” continues Novella.

In the current study, the researchers, together with colleagues from the Philipps-Universität Marburg, were able to evaluate the available data on the color characteristics of dragonflies. “By linking changes in species characteristics, such as insect coloration, to environmental changes, we can better understand the causes of biodiversity loss. The goal of our research group at TUM… was to do this contribute. We want to continue this work at the University of Würzburg”, concludes Christian Hof.