This peacock moth is strikingly colored. But the butterfly differs from its close relatives in other characteristics – and that makes it interesting for evolutionary biologists: time plays a very special role in the development of this species.
Pink combined with fluffy yellow: The butterfly Dryocampa rubicunda looks like a mythical creature, created for animated fantasy films, and only appears at night. In contrast to its more inconspicuous brown relatives from the genus Anisota: This is active during the day or at dusk, depending on the sex.
This makes the butterflies from the peacock moth family, which are only the size of a bumblebee, a prime example for researching how species arise. In the course of evolution, one species becomes two when, for example, populations develop independently of one another over a long period of time, separated by mountains, bodies of water or structural interventions by humans in the natural landscape.
In this case, however, it is not a spatial separation that is responsible for the new branch in the family tree of the peacock moths, but rather, surprisingly, the specific chronobiology: In the “Proceedings B” of the British Royal Society, US scientists from Florida now report that a so-called disco gene (for “disconnected”) controls the day-night rhythm of the butterflies studied differently in each case.
Around 3.8 million years ago, mutations in this gene probably led to the development of a nocturnal, now colorful species with poor eyesight but a keen sense of smell.
The team around Yash Sondhi, who is now at the Florida Museum of Natural History in Gainesville, chose two closely related peacock moths for the study. Their distribution areas in the southeastern United States overlap, but the moths are not competitors for food: the caterpillars of the fabulous Dryocampa rubicunda feed on maple leaves, while those of the orange, brown and pink Anisota virginiensis of oak leaves.
“These two are very similar,” butterfly expert Sondhi is quoted as saying in a statement. But they differ in their flight time. “I was looking for differences in color vision. Instead, we found some in the ‘clock genes,’ which makes sense in retrospect,” says Sondhi.
So-called clock genes control the circadian rhythm of plants and animals. The respective “ebb and flow”, i.e. the increasing and decreasing amounts of proteins formed according to their blueprint, causes cells to become either active or inactive. They influence the entire organism, i.e. metabolism, body temperature, cell growth.
23 mutations in the disco gene
The analyses of the genetic activities also revealed that the nocturnal pink maple moth, which is the only species in its genus, puts more energy into its sense of smell, while the oak specialist promotes the sense of sight. But much more interesting was the disco gene, which is twice as large in the peacock moths as its counterpart in the fruit flies.
By comparing the DNA sequences, the researchers found that the two closely related butterflies differ from each other by 23 mutations in active regions of the gene. Sondhi calls the observed changes “evolution in action.”
“If this is confirmed functionally, this is a really concrete example of the mechanism behind specification at the molecular level, which is rarely found,” said the biologist.
with dpa
