Nature: Mimicry proves best form of defence

This is the ability of a species, evolved over thousands of years, to resemble another species or nearby object, often taking on the appearance of anything from leaves to rocks.

While camouflage assists organisms to blend into their habitats to surprise prey and avoid predators, there are those for which this improves their ability to catch prey or ward off rivals.

Natural selection has seen species develop distinct types of mimicry.

While some katydids exhibit homotypism resembling a leaf, with elaborate wing veins completing the effect, others, including the monarch caterpillar, display automimicry - when an animal mimics itself or its own species.

Although monarch caterpillars have tentacles on the front of their bodies to aid them in feeling surroundings, they also have tentacles on the back to confuse predators and give them time to escape if attacked.

Meanwhile, Mullerian mimicry is defined as when two different well defended animals resemble each other, such as monarch and viceroy butterflies, both of which store noxious chemicals in their bodies from the host plants they eat as a caterpillar.

However, by sharing a color pattern, naïve creatures which consume one or other of the butterflies will learn to avoid the orange and black pattern, meaning both species are protected.

Last year marked the 200th anniversary of the birth of Henry Walter Bates, an English naturalist who formally introduced mimicry as a scientific concept.

In the Batesian form of mimicry, a harmless or poorly defended species mimics the appearance of a more dangerous or toxic species to discourage predators, relying on deception to avoid attacks. One such example are hoverflies, which despite lacking the sting of bees and wasps, have a black and yellow band pattern.

The aim of the study was to discover the genes controlling these similar mimicry colour patterns among seven distantly related species.

The scientists, including researchers from a number of South American countries, found that despite being very distantly related to each other, the various butterfly and moth species reused the same two genes - ivory and optix - to evolve near identical colour patterns.

The genetic changes in the different butterfly species did not happen in the genes themselves, but in similar ‘switches’ that turn the genes on or off.

The moth species surprisingly used an inversion mechanism - a large chunk of DNA flipped backwards - a near identical genetic trick used by one of the butterflies.

Professor Kanchon Dasmahapatra, from the University of York’s Department of Biology, said: “Convergent evolution, where many unrelated species independently evolve the same trait, is common across the tree of life. But we rarely have the opportunity to investigate the genetic basis of this phenomenon.

“Investigating seven butterfly lineages and a day-flying moth, we show that evolution can be surprisingly predictable, and that butterflies and moths have been using the exact same genetic tricks repeatedly to achieve similar colour patterns since the age of the dinosaurs.”

The research, published in the journal PLoS Biology, shows that evolution isn't always a roll-of-the-dice, but can be more predictable than previously thought.

Professor Joana Meier, from the Wellcome Sanger Institute, said: “These distantly related butterflies and the moth are all toxic and distasteful to birds trying to eat them.

"They look very much alike because if birds have already learned that a specific colour pattern means “do not eat, we are toxic”, it is beneficial for other species to display the same warning colours.

“Here, we show that these warning colours are particularly ideal as it seems quite easy to evolve these same colour patterns due to the highly conserved genetic basis over 120 million years.”

Knowing that nature follows a particular route, and is not as random as once thought, helps scientists predict how other species might adapt to their environments, or climate change.