How does mimicry work

And while Batesian mimics often stop at looking like the model species, some mimics take Batesian mimicry to the extreme by mimicking even the behaviors of the models: mimicking sounds, flight patterns and antennal movements. Some organisms mimic something completely different from them, like katydids and moths mimicking leaves, or caterpillars and stick insects mimicking twigs.

The margay Leopardus wiedi i — a small wildcat from the Amazon — mimics the distress cry of a baby tamarin monkey in order to reel in its favorite food. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar.

Mobile Newsletter chat subscribe. Life Science. A hornet moth Sesia bembeciformis , right, mimics its lookalike, the European hornet Vespa crabro in an attempt to keep predators at bay. Now That's Interesting. But this would not necessarily be the primary reason why unpalatability evolved. Individual benefit would explain why relatively solitary larvae, like the famous monarch butterfly Danaus plexippus and many Heliconius are unpalatable. Almost all the monarchs Danaidae are highly unpalatable, yet they all have solitary larvae, and spend their whole time as adults migrating hundreds, even thousands of kilometres, as though to be as far away from their relatives as possible.

So unpalatable species should be especially commonly found living gregariously. They are indeed often found gregariously, as larvae, usually but not always because they were originally laid as a single clutch of eggs by a single female. But they are also often found in aggregations as adults. North American Danaus butterflies fly south to Mexico in winter, and roost in enormous overwintering aggregations of tens of millions of individuals. Kin selection may help in the evolution of unpalatability, as Fisher suggested, but aggregations are not good evidence that it is at all necessary!

Aggregating behaviour of unpalatable species probably evolved after the evolution of unpalatability. Warning colour has rather different evolutionary dynamics, as we have already mentioned. Our species will be assumed already unpalatable due to a sting, or to the sequestration of unpalatable chemistry from a host plant. There may be costs due to the production of warning colours, though we can reasonably assume that bright colours are about as cheap as the browns and greens of camouflaged species -- very different from the assumed costs of sequestration of nasty compounds.

Then, as in unpalatability, there are costs due to teaching predators. These are peculiarly frequency-dependent. When a warning colour pattern element first arises in an unpalatable prey, it should almost always be disfavoured. First, it is more conspicuous to teach better. Second, no predators in the neighbourhood will have encountered the new pattern, so they will be naive; they will remember the old pattern somewhat, even if not very conspicuous or memorable. Suppose the new pattern gets commoner, a strange thing happens.

It becomes better to have the new pattern than to have the older, now rarer pattern: the newer pattern is now the pattern that predators do recognize after a bit of learning, that is. Thus we have a special kind of frequency-dependent selection against rare forms.

Whereas it is possible to interpret a newly evolved warning pattern as an altruism, a common warning pattern is hardly an altruism, because it pays to have it. When the trait is common, it would NOT pay to cheat.

This is very different from helping at the nest, in which benefits and costs, at least within a family of specified relationship do not depend on the population frequency. It is also different from unpalatability, where, if it is altruistic, cheating may pay at high population frequency as we have seen. It is therefore simpler to think of warning colours as a frequency-dependent trait with a disadvantage to rarity, rather than to think in terms of altruisms.

The difficulty for the evolution of warning colour pattern is that selection is conservative, and acts against the novel pattern, even if it is a better warning signal. For example, below is a simple one-locus frequency-dependent fitness function: we assume that frequency dependent selection is linearly related to the frequency, with coefficients s and t actual warning colour will have a more complex, non-linear function!

So how do novel warning colours evolve? If they are always selected against when rare, it is hard to imagine how a new warning colour evolves; whether in a cryptic species or an already warning coloured one. Although not exactly an example of a true altruism, a kin selection model or at least an example of selection acting in groups of kin may work, and was proposed in the s.

If a mutant phenotype A exists, it is more likely to be present in close kin than elsewhere. The new pattern might evolve locally, in groups of close kin, and then spread out to other groups. If you are quick, you will have noticed that this "kin-selection" model is just a special case of the shifting balance. The first mutant will usually lack any family members with the new pattern, unless it is lucky to be a mutation early on in the mother's germ line. Normally, to have several local family members with the same allele, the mutant has become locally common, i.

There are subtle differences, but essentially Phase II is now necessary, where selection increases the pattern locally provided it has crossed the adaptive trough, or threshold frequency. In Phase III, the new pattern will expand its range if fitter, either because it allows a greater population size and therefore causes emigration; or behind a moving cline.

Warning colours can also evolve by individual selection. You will have noticed that many palatable butterflies are already brightly coloured peacock, red admiral in your garden. This can be because they signal to each other for sex - in fact butterflies formed a large section in Darwin's book on sexual selection. Or they might signal to predators, via flash coloration , or because they are Batesian mimics. If these brightly coloured butterflies were to suddenly become unpalatable, perhaps because of a switch to a new host plant, they would be preadapted to warning coloration.

Finally, any of these warning patterns might become enhanced by sensory bias, exactly as in sexual selection. For example, a flash-coloured moth might develop colours similar to the flash colours on the dorsal surface of the forewings, as well as the hidden hindwings, so enhancing the pattern. Most warningly coloured species belong to whole families that are unpalatable and warningly coloured, so that it will probably be impossible to work out exactly how the first species of the group, now probably extinct, evolved warning coloration.

But a noticeable thing about warningly coloured clades is the diversity of warning patterns they present. We have already talked about warningly coloured races within species - these are very common; clearly, the evolution of warning colour is happening very rapidly, all the time, in spite of the evolutionary hurdles that we see in its way. However, the sheer diversity of colour patterns is very hard to explain solely by a deterministic process such as mimicry, which by definition reduces pattern diversity.

Instead, a minority of species, the models, must undergo enough random divergence, perhaps triggered by the shifting balance at least according to Mallet! A harmless snake might have the same markings as one that is venomous. A flower blossom might even look like a fly. This can act like camouflage — make the mimic fade into the landscape — or it can enable an organism to frighten potential enemies or attract gullible prey.

Sometimes such mimicry is flabbergasting. The walking stick, an insect native to Australia, looks so much like a small branch that it is often impossible to spot. But in other cases the imitations are really poor. Most people can tell the difference between a wasp and a yellow-and-black hoverbee.

So how can these juicy an un-stinging flies con predators? Such imperfect mimicry has puzzled scientists for a long time. But Swedish biologists have come up with a reason why certain species get by with a less than identical costume:. Kazemi and her Stockholm University colleagues tested their idea by setting up artificial prey for blue tits. First they trained the birds to catch a number of types of prey of different colours, patterns and shapes and then mimics were presented to the birds to see how readily they learned the difference between good food and non-food.