Butterfly 'eyespots' offer evolution progress

Research into the eyespots found on the wings of some species of butterfly is helping to address fundamental questions about evolution. 

A study from Oregon State University (OSU), published in Proceedings of the Royal Society B, attempts to explain why patterns in nature repeat themselves. The study into investigate these patterns, or serial homologues, and why they are capable of lasting for millions of years across a number of different species.

Groups of eyespots on butterfly wings are serial homologues, as well as rows of teeth and the series of vertebra that form a spinal column. Previous studies have observed the similarities of these patterns and how they change over time, but how they evolved is still unanswered.

Previous theories thought that eyespots evolved from simpler, single spots or that they came from a band of colour.

Jeffrey Oliver, a postdoctoral scholar in the Department of Integrative Biology of the OSU College of Science, concluded that neither of the existing theories are accurate, with the study suggesting that a few eyespots "evolved as a group at about the same time, but behaved somewhat as individual entities".

A product of genetic mutation, the eyespots had the ability to move, which had evolutionary value allowing it to be retained by future generations of butterfly. Eyespots were used to distract predators away from the most vulnerable parts of a butterfly, acting as a bullseye on the wing and diverting them from attacks on the head or body.

However, according to Mr Oliver, the study indicates that further mutation moved the spots to the other side of the wing, where they performed a new function - to attract males.

"If you take this same concept and apply it to other important features like vertebra and a spinal column, it suggests that some small number of bones would form through mutation, and eventually move, join and be perpetuated as they acquired a function with survival value," he added.

He added that over time the vertebra could expand in number, and "acquire other functions" that had nothing to do with their original function, but still had value.