Two species of insects very different from each other have something in common: they used the cortex gene to change their appearances and survive. Two separate studies published Wednesday in the journal Nature revealed how the bright tropical butterflies and the British peppered moths adapted to their changing environment by using different color patterns designed to keep predators away.
Both pepper moths and the Heliconius family of tropical butterflies from South America belong to the Lepidoptera order of insects but scientists did not know that they used the same gene to defend themselves.
However, their specific purposes are completely different. While the cortex gene allows bright butterflies to switch between a wide variety of color patterns that warns predators of their toxicity, it keeps black moths safe as they use it to turn from mostly pale to black in the 19th century industrial Britain in order to camouflage in the lichen-covered tree trunks.
The cortex gene helps educate predators such as birds so they learn they should not eat bright and colorful butterflies because they are venomous, but it also allows pepper moths to go unnoticed.
Both species had been studied for many years, but this is the first time research teams look at the genetic mechanism responsible for the changes in their appearances, according to the co-author of the study focused on the tropical butterflies, Dr. Megan Supple. A postdoctoral student at the Australian National University, she attributed their achievement to the emerging genomic techniques.
What surprised both teams the most was the fact that a single gene was involved in such different survival mechanism, especially because the cortex gene is known for controlling how cells split up and multiply, said evolutionary biologist Chris Jiggins, lead author of the Heliconius research. That means that scientists for the first time discovered the role cortex plays in color variations.
“It’s not a gene you would expect would be involved in this wing color pattern changes, because it’s not a gene that’s controlling the expression of a pigmentation gene,” Supple said. “It’s actually a gene that’s involved in regulating cell divisions,” she added.
They are yet to find out the way cortex regulates pattern and pigmentation, but Jiggins, who is a professor at the University of Cambridge, said the discovery of such a gene being involved in color variation was very important and surprising.
South American butterflies mimic one another to warn predators that they are not tasty at all
Among the rain forests of the American tropics, over hundreds of years, the Heliconius butterfly species have developed a collective form of defense that consists of showing off their bright colors and mimic one another’s patterns. This mechanism is designed to tell predators that they are the wrong meal due to their taste for poisonous plants.
Dr. Nicola Nadeau of the University of Sheffield studied a handful of the 40 Heliconius species. By comparing the genomes of those that did not have a yellow hindwing bar to those that did have it, they found that the gene cortex controlled either the presence or absence of the yellow color schemes, as explained by Dr. Supple.
Pepper moths are rather shy and prefer camouflage
This study says that the dark carbonaria form was first seen in 1848 in Manchester, but the species were not completely unknown by that time. The research team, led by Dr. Ilik Saccheri of the University of Liverpool, found that the species changed its color after a large piece of DNA was inserted into the cortex gene.
The genetic mutation took place around 1819, the researchers estimated after tracing the pepper moth’s family tree. They explain this process exemplifies the industrial melanism, a phenomenon that occurs when species darken in color to adapt to industrial environments.
Prof. James Mallet, who is a specialist on butterfly and moth genetics from the University College London and Harvard University, said the paper focused on the British pepper moths was remarkable and explained how difficult it was to conduct experiments with this species.
“These have been incredibly difficult animals to work with. It’s not easy as a lab animal, it’s hard to breed – it has one generation a year – and it has really limited polymorphism. So it’s very hard to use standard genetic techniques to map the genes and locate them on the chromosomes,” Mallet explained, as quoted by BBC News.
Two friends involved in the studies surprised by each other’s findings
Jiggins and Saccheri were not involved in each other’s research, but they are a couple of friends who turned out to be studying the same gene. The Washington Post reported that they decided to submit their papers to the same journal and publish them simultaneously once they heard of the common element in their findings.
Saccheri was amazed by the fact that both species have not had a common ancestor in over 100 million years and they still conserved the same gene in spite of their differences.
The research teams hope their findings will remark the validity of the natural selection process theorized by Charles Darwin, given that the tropical butterflies and the British moths are a clear example that adaptation means survival.
Source: Washington Post