The ‘disco’ gene could help moths tell time

The planet’s 160,000-plus species of moths are best known for their nocturnal flights and their powerful pollinators. Now some moths are opening an evolutionary window into how one species can diverge into separate species with different traits. The so-called disco gene could be responsible for a major difference in flight patterns in two colorful moths. The findings are described in a study published Aug. 27 in the journal Proceedings of the Royal Society B: Biological Sciences and details how this gene may help regulate day and night flight.

When species diverge

In nature, one species can diverge and become two or more over time. This process is called speciation occurs when individuals from a single population become geographically isolated. The finches of the Galápagos that Charles Darwin studied are among the most famous examples of speciation. About 13 species of finches have diverged from a single ancestor when their populations were spread across different islands and evolved separately. If the populations of organisms remain separated long enough, that will eventually happen lose the ability to cross.

For some mothstheir genetics are influenced by the time of day when they are most active and not by the separation caused by a physical barrier such as an ocean or a mountain range. In this new studythe team focused on two closely related moth species with overlapping ranges in the southeastern United States.

[Related: Moths fight against echolocating bats with sounds of their own.]

Pink maple moths are in the gender Drycampa. They have a thick, fluffy mane above their heads and bellies, with candy-colored pink and yellow scales. Male and female pink moths fly only at night.

Pink striped oakworm moths are slightly less flashy and are members of the gender Anisota. They have more earthy shades of mustard yellow, dark brown and gray. Female pink-banded oakworm moths are active during dusk and early evening hours, while males prefer to fly during the day.

“These two [species] are very similar,” study co-author and Florida Museum of Natural History entomologist Yash Sondhi said in a statement. “They’ve differentiated along this one axis, and that’s when they fly.”

Previous studies showed that both Drycampa And Anisota emerged from one species about 3.8 million years ago. By the standards of evolution, this is quite recent and there are still some important differences and similarities between the two. A handful of species in the genus Anisota are all active during the day, unlike the modern female pink-banded oakworm moths which prefer twilight and nocturnal flying. The nocturnal pink maple moths are also the only known species in the genus Drycampa.

Originally, Sondhi believed that both species of moths would be a good opportunity to investigate how insect vision evolves and when a species changes its activity patterns. However, that wasn’t in the cards.

“I started looking for differences in color perception. Instead, we found differences in their clock genes, which makes sense in retrospect,” Sondhi said.

Genes that ‘tell the time’

Clock genes are specialized genes that control circadian rhythms in both animals and plants. The changes in the proteins that create clock genes cause cells to be active or dormant for a period of about 24 hours. They can also have more than just an impact sleep and wake cycles. Clock genes can influence those of an organism cell growth, blood pressure, body temperatureAnd metabolism and are found in a wide range of organisms.

“It’s a system that can be found in everything from fruit flies to mammals and plants,” Sondhi said. “They all have some kind of timekeeping mechanism.”

[Related: The science behind our circadian rhythms, and why time changes mess them up.]

After finding this one differ in their clock genesSondhi compared the transcriptomes of the two types of moths. Transcriptomes contain only one subset of genetic material and determine when and where a gene is turned on or off in the cells and tissues of an organism. For comparison: genomes contain all of an animal’s DNA. This makes transcriptomes useful in examining differences in an organism’s protein levels throughout the day, as they have more specific information about these proteins.

Sondhi found a number of genes that were expressed at different levels in both moth species. The nocturnal pink maple moths invested more energy in their sense of smellwhile the day-flying oakworm moth produced more genes related to vision.

The disco gene and its ‘zinc fingers’

During this analysis, one additional gene stood out:disco. Abbreviation for disconnected, disco was expressed at different levels during the day and night in both species. Last research on fruit flies thought that disco can indirectly influence the circadian rhythm through the production of the neurons that send clock enzymes from the brain to the body.

The disco gene that was found in the moth samples was about twice the size of its fruit fly counterpart. That was also the case extra zinc fingers. These are active parts of a gene that interact directly with proteins, DNA and RNA. Sondhi believed that the changes in the disco gene were at least partially responsible for the pink maple moth’s shift to night flying.

[Related: Why artificial light—and evolution—trap moths.]

When he got the disco gene of pink maple moths with the disco gene in oakworms, Sondhi discovered 23 mutations separated the two. These mutations were also in active parts of the gene, so they could also potentially contribute to some of the visible physical differences between the moths.

Additional research could also help scientists understand the ways genes change in the wild and how speciation works at the molecular level.