The Atala butterfly (Eumaeus atala) and the five closest relatives of the genus Eumaeus like to display their venom. The poison of this sextet comes from what they eat as caterpillars: plants called cycads that have been around since then before dinosaurs moved on Earth and contain a strong liver toxin called cycasin.
Filled with poison, Eumaeus is big, humble and gloomy and flaps around like they have nowhere to go. Even their caterpillars are conspicuous, gathering in groups to munch cycad plants while sporting a flashy red and gold color. All of their remarkable properties make it known to predators that they are not good food; in nature, being poisonous protects organisms from invading them if known to their predators.
Now, new research led by Smithsonian National Museum of Natural History butterfly curator Bob Robbins tells a evolutionary story of how these six poisonous butterflies got their protection from poisons. as well as the bold colors and behaviors that tell the predators that would lead clear.
Butterflies do not have teeth or talons to protect themselves. But they use their wing color and flight behavior as an indication of their unfavorable qualities to predators, sometimes deceptively and in others in reality, as in the case of Eumaeus. With the modern ability to easily sequence genomes, we have the opportunity to look at that in detail for the first time. “
Bob Robbins, B.utterfly C.urator, National Museum of Natural History, Smithsonian
The paper, published in the February 8 issue of the magazine an Proceedings of the National Academy of Sciences, responsible for 46 butterfly genomes in order, including the six members of Eumaeus and several members of the 1,000-strong butterfly group Eumaeus associated with it – the hair scraps.
Haircuts are widespread in North and South America, and almost all of them are small, vulgar and nondescript. Their caterpillars, which usually eat a mixed diet of flowering plants, are usually camouflaged and do not accumulate in groups.
The ranks of Eumaeus are very special; so much so that some researchers have suggested that a haircut may not be Eumaeus at all. Moreover, due to the ancient evolutionary history of cycads, most scientists had accepted that the six members of Eumaeus developed their tolerance for cycasin and their prevalence over time. great in their history of evolution.
To resolve the issue, Robbins and his colleagues began classifying the genomes of six Eumaeus members and a bevy of other hair strands about three years ago, drawing on the wealth of diverse samples held. in the museum’s collections as well as some symbols from wild butterflies. . These results conclusively showed that the Eumaeus butterflies were not an ancient evolutionary departure from the rest of the males. In fact, they are closely linked to a pair of very common genes called Theorema and Mithras.
The results also showed that the ability to eat poisonous cycads was a stimulus for Eumaeus to provoke a frenzy of rapid evolutionary change that surpassed all other haircuts. The team also learned that Eumaeus had split into two evolutionary lines after they started eating cycads, so they were able to study the evolutionary waterfall twice, taking a look. included the marked genetic similarities that both lines had in responding to their new toxic diet.
When the team began analyzing the Eumaeus genomes, they saw a major genetic shift to parts of the genomes of these butterflies associated with the construction of different types of proteins. To find out whether these proteins may be related to eating cycads, the researchers compared the Eumaeus genomes to butterflies in Theorema, their closest non-toxic relatives. , which has camouflaged, solitary caterpillars that eat a normal range of flowering plants.
The theory also had some fast-growing segments of DNA that coded the construction of various proteins. When Robbins and his co-authors compared the two genomes they eliminated areas of rapid change that intertwined between the two in the hope that the genetic changes involved in their dealing with toxins separating the cycad.
“Certainly, there was a basic group of proteins that had gone through a lot of rapid change in Eumaeus but not in the girls who don’t eat cycads,” Robbins said. “When we looked at the action of the rapidly changing proteins, it was very strong on the proteins that would destroy cells, proteins that would remove dead cell debris and proteins to form new cells.”
Robbins said that these proteins are just what an organism would need if it needed to find a way to safely absorb a cycasin – type toxin. “If the cycad toxins were to kill cells at high levels, the organism would have to break down those cells, clean them out and then replace them quickly to avoid any side effects,” he said. e.
This research details the evolution of toxic defense mechanisms in the six butterfly species and the resulting genetic effects. While it may not have been as easy to show warning color and lazy flight in the Eumaeus genes, it did coincide with the change in diet.
Several butterfly species have evolved to make them less attractive to predators by eating poisonous substances, and Robbins said this evolutionary account of how Eumaeus respected his defense may have evolved a evolutionary model. offer for how species adapt to living with these toxins inside their bodies.