Same body, different engine: identical butterfly species shed new light on evolution

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 Christian Ziegler Christian Ziegler

In Central and South America live two different species of butterflies with identically the same pattern on their wings. Eleven million years ago, the two species each went their separate evolutionary paths, eventually arriving at the same solution to deter their natural enemies: a color pattern on their wings that to birds is equivalent to "I’m not a tasty morsel. You would expect the identical physical appearance to have the same genetic engine. But evolutionary biologists from KU Leuven and Puerto Rico, found that’s not quite the case. The research, published in Science, shows that an identical appearance does not automatically mean that the animals walked the same evolutionary path genetically. The research shows that evolution is much less predictable than previously thought.

In nature, everything is about (over)living. Survival of the fittest ensures that animals eventually adapt according to their environment and prey predators present to ensure their survival. "Mimicking other animals with skittish patterns is a great example of this and we would like to better understand this process to gain more insight into the course of evolution that has been going on for millions of years. Yet we sometimes have to conclude that evolution is not a predictable process and thus we can never predict with 100% certainty how today’s animals will adapt to the nature of the future," said evolutionary biology professor Steven Van Belleghem. He and international colleagues from Puerto Rico and Panama, among others, compared the genetics of two butterfly species with the same color pattern on their wings.

Don’t judge a butterfly by its cover

Butterflies often fall prey to birds and will use the colors on their wings to appear larger and more dangerous or to indicate that they don’t taste good. Once birds know which wing patterns mean "I’m not tasty," they will not be quick to eat these butterflies. So for butterflies to have such a ’not tasty’ pattern is a strong evolutionary advantage which greatly increases their chances of survival. This technique is also used by two species of Heliconius butterflies. Although the two different species separated 11 million years ago and followed their own evolutionary path, they have the same wing pattern that to birds means as much as "Don’t eat me because I taste gross.

"It cannot be a coincidence to arrive at the same appearance after 11 million years. So there must definitely be an advantage for the butterfly," said Professor Van Belleghem. "Within evolutionary biology, this phenomenon has been known for some time, but our research wanted to see if, in addition to the similarities on the outside, the underlying genetics are the same. That could teach us what genetic processes drive evolution and allow us to make predictions about animals past and present."

Yet the research results show that the butterflies have fewer genetic similarities than thought. "The butterflies’ genes involved in their wing pattern are regulated in a different way and have different mutations. As if after 11 million years they have arrived at the same body but under the hood a completely different engine drives the whole process," Van Belleghem concludes.

The study concludes that adapting one’s appearance to the environment is a regular occurrence in nature but the evolution toward it is unpredictable and can happen through different genetic mechanisms. Nature is not quite giving up its secrets for now.