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How does natural selection produce mimetic traits?

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Müllerian mimicry: butterflies — mimicry *Heliconius* butterflies demonstrating Müllerian mimicry, a form of mimicry where one or more species exhibit closely similar warning systems. In this case, wing patterning and coloration among the species appear very similar.

Natural selection produces mimetic traits by favoring organisms that possess deceptive signals—such as appearance, behavior, or sound—that provide a survival advantage when perceived by a third-party receiver, typically a predator.12

The evolutionary process often begins with an incipient stage of resemblance, where preexisting species-specific features provide a nondirected, preadaptive by-product that happens to deceive a receiver. Once this initial resemblance exists, it creates a point of attack for new selective pressure, refining the signal over time.3

The mechanism of selection depends on the type of mimicry:

Batesian mimicry: A palatable species evolves to resemble an unpalatable or dangerous model. Natural selection favors this resemblance because it deceives predators into avoiding the mimic. If the mimic becomes too abundant, however, predators may learn to associate the signal with palatability, which can then drive the model to evolve a new signal.21
Müllerian mimicry: Two or more unpalatable species evolve to share the same warning signals. This is advantageous because predators only need to learn one pattern to avoid, spreading the cost of "educating" the predator population across multiple species.245

In all cases, the signal receiver—such as a predator—is the primary agent of selection, as its ability to correctly identify or mistake the mimic determines the survival of the sender.31