The convergent evolution of butterflies is controlled by a single gene

Certain butterfly species are poisonous, providing a deadly defense against predators. Over time, different butterfly species have evolved the same color patterns, basically telling predators to avoid all butterflies of that appearance. This is the mystery of convergent evolution.

These butterfly species are only distantly related, and once in their evolutionary history they didn't look anything like each other. However, non-poisonous species evolved wings that mimicked those of their deadlier counterparts, effectively offering themselves the same protection from wary predators that the poisonous butterflies enjoy.

Scientists have been trying to explain how this works for the last 150 years. Now, thanks to new research by UC Irvine's Robert Reed, we may now have an answer. It all comes back to a singe gene known as optix, which controls the red wing color patterns in lots of distantly related butterfly species.

Reed, whose specialties include ecology and evolutionary biology, explains:

"This is our first peek into how mimicry and convergent evolution happen at a genetic level. We discovered that the same gene controls the evolution of red color patterns across remotely related butterflies. This is in line with emerging evidence from various animal species that evolution generally is governed by a relatively small number of genes. Out of the tens of thousands in a typical genome, it seems that only a handful tend to drive major evolutionary change over and over again."

The researchers crossbred butterflies over several years so that they could track how the color pattern genes were expressed. By mapping the different butterfly genomes, they were able to identify a strong correlation between red color patterns and one small area of the genome, which is how the gene optix was identified. They were then able to confirm this breakthrough by studying genes in hybridization zones, where different butterfly species naturally interbreed. Once again, the optix gene was crucial to the development of the color patterns.

Reed explains what this means, and where he hopes to go next:

"Biologists have been asking themselves, 'Are there really so few genes that govern evolution?' This is a beautiful example of how a single gene can control the evolution of complex patterns in nature. Now we want to understand why: What is it about this one gene in particular that makes it so good at driving rapid evolution?"

Via Science. Image by Durrell Kapan.