Scientists discover genetics behind how butterflies can disguise themselves as leaves

Scientists are hailing a newfound understanding of how butterflies are able to use their wings to camouflage themselves to look like leaves.

Kallima – also known as “oak leaf” – butterflies are among the most well-known and striking examples of animals which use leaf mimicry to protect themselves from predators.

They do so by flapping their vibrant blue, black and orange wings to reveal dull brown undersides strongly resembling dead, decaying leaves.

The tactic is so effective that famed 19th-century naturalist Alfred Russel Wallace, who collected the insects in southeast Asia while advancing his and Charles Darwin’s theories of natural selection, described it as “the most wonderful and undoubted case of protective resemblance in a butterfly”.

While the former’s work has been contested for decades, with many geneticists insisting that these butterflies’ camouflage abilities are more likely to be the result of sudden mutations than gradual evolution, the new findings appear to lend fresh weight to Wallace’s argument.

The researchers now believe they have discovered the gene responsible for leaf mimicry in Kallima butterflies.

In research published this week in the journal Cell, the team collected samples from 36 different types of Kallima butterflies at 11 locations across east and southeast Asia. Using genome sequencing, the scientists then honed in on one specific gene named “cortex” – which they found appeared to be responsible for the varying leaf-like patterns in their wings.

“Butterfly wings have relatively simple structures, but this simple structure is responsible for some very complex functions: locomotion, thermoregulation, mate preference, and predator avoidance,” said one of the study’s co-authors, Wei Zhang, a butterfly researcher at Peking University.

“Because these wings are structurally simple but functionally complex, I think butterfly wings are the ideal system to address multiple evolutionary questions.”

The team also explored how the creatures’ genetic diversity has been shaped by climate change and the Earth’s history – arguing that the butterflies’ vast diversification coincided with a period roughly spanning three and 10 million years ago, during the emergence of the Himalayas and Tibetan Plateau.

The creation of these vast mountains diversified habitats for butterflies in southeastern Tibet and the northwest of the Chinese province, Yunnan – creating opportunities for isolation, habitat specialisation, and divergence before the butterflies later dispersed across other parts of Asia, according to the study.

Because they found so much variation in this area of the eastern Himalayas, they were able to examine the butterflies’ evolution on a smaller scale than usual.

“We generally focus on biodiversity at a macroevolutionary level,” said Ms Zhang. “But we seldom have cases that illustrate in detail how species diversity and genetic diversity originated in such a diversity hotspot.”

In the future, the team intend to continue to examine how wing colouration and patterns vary in different regions and with different plant life, according to Ms Zhang, who said: “We would like to understand how these genes facilitate, and originated, such beautiful diversifying wing patterns.”