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Scientists discover gene responsible for butterfly camouflage

Researchers say they found the gene that gives oakleaf butterflies the ability to mimic and camouflage their wings to look like leaves and other foliage.

(CN) — The high valleys of the eastern Himalayas offer breathtaking views and a hotspot of biodiversity. Within this vast region, scientists say they discovered something remarkable hiding in plain sight.

The landscape is home to many kinds of oakleaf butterflies – the species can be found across Asia – but there is one quality that aides their survival in such a large yet harsh environment. Their radiant color patterns contrast from a deep blue, orange, and black to an underside that looks like a dull dead leaf, helping them hide from predators.

Wei Zhang, a butterfly researcher at Peking University in China and co-author of a study published Monday in the journal Cell, described in an interview how the species developed its mimicry and camouflage ability.

“Kal­lima butterflies are a representative example,” of developing a quality that is “driven by natural selection” she said, using the scientific name Kallima inachus.

The oakleaf butterfly is “regarded by [British naturalist] Alfred Russel Wallace as 'the most wonderful and undoubted case of protective resemblance in a butterfly,'" Zhang said, making these butterflies the ideal specimens to study complex evolutionary innovation as it adapts to geographic change.

Zhang said it was the broad range of samples from many different teams working in the field, across the continent, that led to the discovery of the gene that allows the oakleaf butterfly to mimic leaves.

The team saw the eastern Himalayas as a focal point of diversification of the species. To understand how these butterflies developed such different and distinct looks, the team collected samples of 36 different types of categories of oakleaf butterflies from an area that includes Northern India, Nepal, Bhutan, Bangladesh and China. 

Kallima butterfly wings shown from the top side and under side. (Cell/Wang et al.).

By sequencing the butterfly’s genome, they were able to find a gene called, Cortex, which appears to be responsible for the leaf mimic ability.

The natural camouflage, Zhang said, shows how “developmental constraints can be reconciled with evolvability.” The longitudinal study that began in 2015 required a lot of field collection and then rearing and caring for the butterflies in a lab. It was during this collection phase of the research that Zhang said the team found something interesting.

“We discovered during specimen collection that multiple species can be collected in the eastern Himalayan region, which gave us much inspiration to come up with a hypothesis for their speciation," she said, adding there was a clear indication that different habitats played a role in how their camouflage ability developed.

“During the rearing of these butterflies, we found that the leaf wing polymorphism is a Mendelian trait, which provided us with clues to further investigate its genetic mechanism,” Zhang said, referring to the process of how dominant and recessive genes can arise over time in alternative forms.

The camouflage trait seems to balance itself in a population, as too much of a good thing can be a problem in evolution.

“If too many individuals in a population exhibit a certain leaf wing phenotype, the effects of this leaf mimicry are reduced, making Kallima butterflies easy for predators to recognize," Zhang said.

She said this type of research is an important way for scientists to identify “some toolkit genes that are repeatedly favored by natural selection and play an important role.”

With certain species losing habitat or becoming endangered, Zhang said, “studies on the population dynamics and diversity of butterflies will help people better understand their current status, as well as that of the vegetation associated with them."

“In addition, the biodiversity hotspots involved in these studies are also worthy of attention," she said.

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