The dead leaf butterfly’s “gift” gene that mimics leaves has been found

Dead leaf butterfly Photo by Zhang Yubo

The Chinese subspecies of the dead-leaved butterfly has a ventral and dorsal wing, and its ventral surface exhibits a leaf-shaped phenotype with bright orange patches on the underside of the wings. Courtesy of Zhang Wei

The wings of the dead leaf butterfly are perfectly mimic a dead leaf, which in turn helps it camouflage to avoid predator attacks. What gives it this “talent”?

Now that the team of Wei Zhang, a researcher at Peking University’s School of Life Sciences, has uncovered the secret, she and her collaborating team have discovered genes that help dead leaf butterflies mimic leaves, and discussed the background and significance of this evolution. The study was published on the cover of the journal Cell on August 1.

Zhang Wei believes that the butterfly wing structure is relatively simple, but it can achieve some very complex functions: movement, body temperature regulation, mate preference and avoidance of predators. “Because these wings are simple in structure and complex in function, butterfly wings are an ideal system for solving multiple evolutionary problems.” She said.

The back of the wings of the dead leaf butterfly is brightly colored and features dark blue, black and orange. But when they flap their wings, they reveal contrasting ventral colors — patterned elements similar to mid-veins, secondary veins, petioles, and variable markings similar to mold spots. In this way, it can mimic a dead leaf.

In order to understand how the camouflage ability of the dead leaf butterfly evolved and inherited, Zhang Wei’s team resembled the genome of 105 butterfly specimens in a total of 21 genera by collecting 13 geographical population samples of the genus Dead Leaf Butterfly and other butterfly family samples, tracing the origin of the genus Dead Leaf Butterfly.

It is worth noting that the research team did not collect specimens of the genus Butterfly in the famous Butterfly Valley of Yunnan, only the cryptophytic leaf butterfly in Ruili, Yunnan, while in Metuo County, Tibet, it collected three species of dead leaf butterflies: the blue ribbon leaf butterfly, a subspecies of the finger-spotted leaf butterfly, and the cryptophyllary leaf butterfly.

They focused their attention on the eastern Himalayas, where they found a large number of butterfly wing pattern changes, allowing them to study population evolution on a smaller scale. “We usually focus on biodiversity at a macroevolutical level, but there are few cases that can elaborate on how species diversity and genetic diversity originated in such a diversity hotspot.” Zhang Wei said.

Biodiversity includes species diversity, genetic diversity and ecosystem diversity, and its genesis is one of the core issues in biology. In the terrestrial environment, mountain ecosystems contain unusually diverse terrestrial biodiversity, and scientists believe that the potential reasons for this include the formation of a diverse microenvironment caused by huge elevation gradient changes, which promote the differentiation of populations. In the study, the authors suggest that the eastern Himalayas may be the origin and differentiation center of the butterfly of the genus, and that the uplift of the Tibetan Plateau may promote species differentiation within the genus.

So, what causes the change in the pattern of different “leaf” patterns on the ventral surface of the wings of the dead leaf butterfly? The researchers performed genome-wide association analysis of 10 leaf-shaped phenotypes by focusing on the Chinese subspecies of the dead-leaved butterfly, based on second-generation genome resequencing data from 78 individual samples, and finally locked in a gene called cortex, which appeared to be associated with different leaf patterns, and found that it underwent long periods of equilibrium selection in multiple species.

“Cortex is like a ‘toolbox gene’ in wing development, involved in controlling developmental processes such as biological form and structure, and in the Chinese subspecies of the dead leaf butterfly, its chimeric deletion mutations will appear mottled phenotype.” Zhang Wei explained as China Science Daily.

It was found that the polymorphism of leaf shape mimesis of dead leaf butterflies arose before species diverged within the genus, and that the evolutionary pressure of genes drove interesting morphological changes in the wings of butterfly populations. “This winged polymorphism has been maintained in multiple dead leaf butterfly species, but different species may have different phenotypes. I think this is due to the proliferation of specific plants in specific habitats, so butterflies get more protective benefits through different wing patterns. Zhang Wei said.

It is understood that the study took about seven or eight years from conception to publication, of which large-scale research work began in January 2018 when Zhang Wei returned to Peking University from the University of Chicago to establish a laboratory. The authors say the study provides a new perspective for understanding evolutionary innovations driven by geographic change and natural selection, and provides new theories and paradigms for biodiversity research.

In the next step, Zhang Wei’s team intends to continue to study how the color and pattern of butterfly wings change in different regions and different plant distribution ranges. “We wanted to know how these genes contributed to and originated from such complex and beautiful wing patterns.” She said. (Source: China Science Daily Feng Lifei)

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