100 million years ago we experienced a unique and unrepeatable evolutionary event: the appearance of butterflies

The butterflies (rhopalocera) are one of the insects that generates the most admiration among locals and strangers thanks to the striking colors that make many of the nearly 2,000 species grouped in this category so attractive. They are cousins ​​of moths (together they form the group Lepidoptera (Lepidoptera)), forks precisely this fork between both groups where a great mystery has been solved.

The key difference between moths and butterflies is their tendency towards nocturnal or more diurnal habits. This factor is behind, for example, the diversity in the colors of some and other species. 100 million years ago a simple change in flight cycles of the American moths would have been the great event that gave rise to the appearance of butterflies.

We know this thanks to one of the largest genetic studies carried out on species of this family. A study that has also helped to understand which plants were instrumental in this evolution.

The evolutionary history of these animals has had to be rewritten over the yearsand it is that until very recently the evolution of these animals was believed to have been relatively recent.

The dominant hypothesis until now explained the evolution of butterflies as a consequence of ecological pressure, especially that caused by the bats, flying mammals and nocturnal hunters that often make moths their prey. The moths may well have switched to a daytime schedule to escape these predators.

However butterflies and moths would have diverged long before the appearance of chiroptera or bats, about 50 million years ago. Somewhat after the Cretaceous-Paleogene mass extinction, and long after the appearance of the first butterflies, an event now estimated to have occurred 100 million years ago.

The “evolutionary explosion” of butterflies occurred in that period of time in which butterflies and dinosaurs coexisted. Almost all the key branches in the evolution of these insects had already been established and, perhaps most curiously, had begun to engage in a curious “affinity” with a specific group of plants: Fabaceous plants responsible today for giving us beans.

Another important factor would have been the appearance of bees. The dominant hypothesis today ensures that bees evolved in parallel, symbiotically with the flowers of plants. The butterflies could have taken advantage of this to find an important food source in the nectar.

“We observe this association over an evolutionary time scale, and in virtually every family of butterflies, [las fabáceas] They appeared as the ancestral guests. explained in a press release Akito Kawahara, co-author of the study. “This was true for the ancestors of butterflies as well.”

2,000 species of butterflies

In their analysis, Kawahara and his team studied the DNA of 2,000 species of butterflies, representing 92% of known genera. They also had the opportunity to compare these data with 11 fossil specimens.

Fossils of these animals are extremely rare due to their delicate wings and their ease in decomposing without a trace. Details of the study conducted by the team were recently released. published in an article in the magazine Nature Ecology & Evolution.

The evolutionary history drawn by these researchers it also has to do with its geographical expansion. The butterflies would have arisen in the South American continent, then closer to Africa than to North America.

However these insects would have taken this northern route to get through the Bering Passage to Asia. From there they would have spread, now, to Africa, as well as India, which at that time was still adrift, far from Asia. In the same way they would have reached Oceania, a continent that had just “detached” from Antarctica.

Europe would have been the continent forgotten by these animals. As the authors of the study point out, the “old continent” does not have a great diversity of butterflies and those that inhabit it are not endemic to it, but can be found in other places. This would fit with the evolutionary history deduced by the study.

In Xataka | There is an amazing “arms race” between bats and moths: science has studied it closely

Image | Lenstravelier