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Butterfly eyespots have potential

By Paul Robinson - 28 May 2014 11:29:0 GMT
Butterfly eyespots have potential

The butterflies in this study can have lots of eyespots or not. Here is the northern pearly eye with eyes on both the upper and lower wing surfaces; Butterfly image; Credit: © Shutterstock

The nymphalid butterflies are among the most admired, not least for their eyespots. These are examples of repeated characteristics in a phenotype that can even remove to different parts of the body. Analysing 400 butterflies, Jeffrey C. Oliver and his colleagues found there was evidence for various redeployments of the original wing eyespot genes away from their original predator distraction function for use in sexual signalling in other body locations. Our example here is the North American Enodia anthedon which is shown to have eyespots in all of its wing sectors. The common name is the northern pearly eye.

Limbs, teeth and vertebrae all use a serial formation pattern in different species. The gene regulatory network is regulated by external signals to produce the required end-result. Modification and elimination have caused our own and other species' bodies to shape up the way they are. This paper tests whether the structures were originally a single unit or already a repeated series of units, or "eyes." These characteristics are ancient so the serial effect is visible in any recent species. The vertebrate limb originated as paired anterior fins, and was then transferred to the posterior for the hind limbs to be formed. The evolution of Nymphalid eyespots is quite recent, so they serve as an excellent example of a serial characteristic.

Concentric rings of colour seemingly began to appear in wings of the Nymphalidae about 90 mya. Either they began as a band of colour that were constricted at the veins of the wing or they were "co-opted" from one sector of the wing into others. To investigate this 349 nymphalid spies were investigated, along with a few other species. In this way, all relatives were checked, or at least the close relatives of those left out! It turned out that the ancestral type was eyespots (4 or 5) occurring only on the underside of the hindwing. Eunica viola and Panacea regina are modern examples of this type of pattern.

Gain or loss of eyespots took place several times in the species of the Nymphalid family, in both sexes. They were lost more frequently than they were gained, probably because the developmental change of a gain is more complicated. A loss would simply need a single change such as one mutation. The same genes of course can be involved even in quite distant relatives.

As a prime example of trait evolution, nymphalids have shown individuation.(individual regulation) Turning the eyespot on and off is the only example of this effect, as the size and colour composition also vary in the wing sectors. Now we need to find the switches that turn the eyespot on and off. The potential is in eventually exploring the teeth, the vertebrae and the teeth switches in the more advanced vertebrates. Starting small means we can slowly achieve great results with the biggest organisms

Jeffrey C. Oliver and the other authors from Yale, Oregon State, Tennessee and Singapore Universities publish this significant paper today in the Proceedings of the Royal Society B: Biological Sciences.