The Elements of Evolution (49-11-1) Batesian Mimicry

 Batesian Mimicry

In 1848, English entomologist Henry Walter Bates went to the Amazon on an expedition to study life there. His was the first scientific account of animal mimicry, particularly the type that bears his name: Batesian mimicry, which is phenotypic imitation by a palatable species of another that is noxious.

Bates found numerous examples of innocuous butterflies with wing patterns that mimicked species unpalatable to would-be predators. He called them “mockers.”

Longwings, the Batesian butterflies, speciated by mating preferences for specific patterns. The gene for wing color is inherited along with the mating choice. Different species are still able to interbreed but choose not to.

Such speciation is a 2-step process. 1st, populations isolate behaviorally: choosing not to mate based upon cosmetic genetic expressions, such as a wing pattern in the case of longwing butterflies. Once separation is well-established, more extensive genetic modifications occur, sometimes rapidly, to optimize the new species to its situation.

The hoverfly is stingless. Its coloration mimics wasps and bees that carry the potential for a painful prick. This gives the hoverfly adequate protection without incurring the cost of carrying a stinger.

Mimicry need only be as precise as the key signals that the target audience relies upon for recognition. Typically, coloration is critical.

Flies that mimic wasps or bees do so only to the degree that it confers sufficient protection. Because birds prefer snacking on larger flies than smaller one, larger mimics are better imitators. The little flies simply aren’t under enough pressure to evolve perfect disguises. Mockers work the essentials into their act while letting the rest slide.

Wasps kill large numbers of other insects. Many wasp mimics evolved to avoid being eaten by predatory wasps rather than by educated vertebrate predators. ~ German entomologist Michael Boppré et al

The essentials change if the mimicked model becomes scarce or disappears entirely. Venomous coral snakes disappeared from an area in North Carolina around 1960. The local harmless kingsnakes that mimicked coral snakes quickly adapted to become a more precise imitation of their model, so that potential predators would not make the mistake of thinking them fake. Scarcity in the real thing incited better precision in the fakes.

Only the most precise mimics are favored as their model becomes increasingly rare. ~ American zoologist Christopher Akcali & American biologist David Pfennig