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Seeking clues to natural selection in butterfly wings

Batesian mimicry is the concept that animals imitate one another for an evolutionary advantage. Today, scientists know that Batesian mimicry exists in many animals, from frogs and snakes to birds and bees and, of course, butterflies. And now a team of researchers is using its understanding of this fundamental evolutionary mechanism, along with modern genetics techniques, to answer one of the biggest, most basic questions in biology: How do new species form? To answer this question, the researchers studied mimicry in a pair of butterflies -- one toxic, one tasty -- that look alike but are only distantly related. The toxic butterfly, or "model," is Adelpha californica, commonly known as the California sister. The mimic, which tastes fine and is harmless to birds but sports bright red-orange spots that make it look like the toxic model, is Limenitis lorquini, or Lorquin's admiral. In a California study area, where the model butterfly is very common, the scientists found that Batesian mimicry worked as predicted: Birds attacked the model and the mimic less often than they attacked either control. And in an Idaho site, where the model is usually absent, birds attacked the mimics and controls at about the same rate, as expected. Having confirmed that Batesian mimicry is indeed at work with these butterflies, the scientists are now moving on to the genetic portion of the work. Understanding the gene flow of these small traits in butterflies may deepen understanding of the evolutionary diversity at large, and help answer some questions about how we came to be.

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