Mystery of dragonfly color solved by scientists

For more than 20 years, a research team from Lund University in Sweden has been studying the common damselfly. Females occur in three different color morphs – one with a masculine appearance, something that protects them from mating harassment. In a new study, an international research team discovered that this genetic variation in color shared across multiple species arose through changes in a specific genomic region at least five million years ago.

The question of how and why genetic variation arises and is maintained over long periods of time is of fundamental importance to evolutionary biology, population genetics, and conservation biology. In all populations of limited size, genetic variation is lost over time. It is therefore important to understand both the mechanisms that give rise to new genetic variations and the mechanisms that act to maintain the variation. This has significance for both species conservation and the future evolutionary potential of populations to adapt to rapidly changing environments.

In the new study published in Nature Ecology and Evolution, a research team has mapped the extensive and striking color variation among female blue-tailed damselflies (Ischnura elegans).

“In this species of damselfly, there are three genetically determined color forms in females, one of which makes them appear male. These male-like females have an advantage because they avoid excessive mating harassment from males. Our study sheds light on when, how and why this variation arose, and shows that this variation was maintained over long periods of evolutionary time through so-called balanced natural selection,” says Erik Svensson, professor of biology at Lund University.

By sequencing the DNA of the three colored forms of the blue damselfly and comparing it to the two colored forms of its closely related tropical relative, Ischnura senegalensis, researchers were able to demonstrate that this genetic color variation in females arose at least five million years ago. years. ; through several different mutations in a specific genetic region on the damselfly’s thirteenth chromosome.

“The wide variation in color in insects fascinates the general public and raises questions about the function of color signals and their evolutionary consequences in mate choice and conflicts between the sexes,” says Erik Svensson.

Having located the gene behind female color variation, researchers can now go further and identify different genotypes in the males and in the aquatic larval stage of these insects. Males do not have visible color forms, but researchers plan to investigate whether the color gene affects other characteristics of larvae and males, including survival and behaviors.

“We now have a good knowledge base to investigate color variation over longer evolutionary timescales among other species of this genus of damselfly, which occur in Europe, Africa, Asia, Australia, North and South America. These “New genetic results help us understand both the evolutionary processes that occur within a species and what happens on longer macroevolutionary evolutionary timescales of tens of millions of years and across many different species,” concludes Erik Svensson.