Many researchers thought butterflies first evolved in Asia, but a global genetic analysis suggests they arose in North America, well before the non-avian dinosaurs went extinct.
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| A black swallowtail butterfly Shutterstock / KathereneS |
Butterflies first fluttered onto the scene in North America about 100 million years ago, according to a genetic analysis. The findings have been used to generate a detailed butterfly family tree, giving scientists new insights into butterflies’ evolutionary origins and how they spread across the world.
“The family relationships and the history of butterflies, surprisingly, is not very well known,” says Akito Kawahara at the University of Florida.
Previous smaller-scale projects had attempted to pin down the insects’ most ancient ancestors, says Kawahara. There were also hypotheses about butterflies’ geographic origins, but no one had narrowed it down.
Kawahara and an international team of researchers gathered data on butterflies from all over the world, using specimens in 28 different museum collections. He and his colleagues analysed 391 genes from nearly 2300 butterfly species. The species came from 90 different countries and represented 92 per cent of all known butterfly genera.
Pável Matos-Maraví at the Czech Academy of Sciences says he is impressed by the “unprecedented amount of data handled” in the study.
The researchers used genetic analysis to date when butterfly groups split apart from each other, and determined the most likely geographic origin of the first butterflies. The team estimates the earliest butterflies evolved about 100 million years ago.
This confirms earlier research that suggested the delicate nectar-sippers arose in a similar time period. Butterflies evolved from nocturnal moth ancestors following the proliferation of the first flowering plants during the Early Cretaceous period, exploiting the new food resource and taking advantage of the co-evolutionary relationship that was already forming between flowering plants and bees, says Kawahara.
Butterflies’ debut appears to have occurred in North America, amidst a backdrop of bony-plated herbivorous dinosaurs and fleet-footed, fluffy ancestors of Tyrannosaurus rex. This was a surprise to Kawahara.
“Some people had thought that because there’s a pretty high diversity of butterflies in Asia, that was the origin,” he says.
From North America, the insects dispersed, first into South America and then westward to Australia, Asia and India, then an island subcontinent. Eventually butterflies flapped their way into Africa, and finally – about 17 million years ago – they arrived in Europe.
The research team also compiled more than 31,000 records of plants eaten by butterfly larvae, reconstructing the evolution of these plants alongside the butterflies. The team thinks that the first butterfly caterpillars munched on plants in the legume family. Today, more than two-thirds of butterfly species limit their diet to plants in the same family, while about one-third are generalists that feed on two or more different plant families. The newly gained knowledge about the evolutionary connections between butterflies and their host plants may be an important resource for butterfly conservation, says Kawahara.
“There are lots of butterflies that are disappearing very fast all over the world,” he says. Having a solid understanding of how dependent they are on certain host plants could inform future conservation efforts.
The findings also reveal that the butterfly family tree may need extensive revision. The researchers estimate that 27 per cent of all butterfly tribes – collections of genera smaller than a family – are mistakenly grouped with others.
Butterflies are highly studied animals, says Kawahara, “but my gosh, we still have a lot of work to do”.
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