Butterfly eyespots reuse genes that pattern limbs and wings

Many species of butterflies use eyespots – circular markings of contrasting colors found on their wings – to intimidate or distract predators. A research team led by the National University of Singapore (NUS) has investigated the evolutionary origins of these eyespots and discovered that they seem to be derived from the recruitment of a complex network of genes which was already operating in the body of the butterflies to build antennae, legs, and sometimes even wings.

“This new study addresses how novel complex traits might originate. These complex traits require the input of many interacting genes for their development, and are often illustrated by the vertebrate eye, or the bacteria flagellum,” said study senior author Antónia Monteiro, a professor of Biology at NUS.

“In our study, we looked at the how butterfly eyespots – an example of a complex trait – came about and concluded that a network recruitment approach is adopted by butterflies for the creation of eyespots. We have also identified the specific network of genes that was likely recruited.”

According to Professor Monteiro and her colleagues, the evolution of new complex traits such as the butterfly eyespots proceeds through mutations in the genetic code that recall pre-existent gene regulatory networks which were already used for other complex traits such as antennae or other limbs. These networks can be compared to subroutines in a computer program that perform specific tasks and, although they are written in the code only once, they are referred to repeatedly by the program as it runs.

By deleting unique DNA regulatory sequences in the genome of the butterflies, the researchers proved that a single gene regulatory network was responsible for the development of a variety of traits, including eyespots, antennae, legs, and wings. When the functioning of this regulatory network was disrupted, all of these highly different traits failed to develop properly.

“It was amazing to observe how these significant complex traits were affected by the same changes in DNA,” concluded study co-author Dr. Heidi Connahs, a postdoctoral fellow studying the evolution of morphological diversity at NUS.

The study is published in the journal Proceedings of the National Academy of Sciences.

Image Credit: Kristof Zyskowski and Yulia Bereshpolova

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By Andrei Ionescu, Earth.com Staff Writer