Flitting among the cool slopes of the Appalachian Mountains is a tiger swallowtail butterfly that evolved when two other species of swallowtails hybridized long ago.
It's a rarity in the animal world, biologists have found.
They discovered that the Appalachian tiger swallowtail, Papilio appalachiensis, evolved from mixing between the Eastern tiger swallowtail, P. glaucus, and the Canadian tiger swallowtail, P. canadensis.
The Appalachian tiger swallowtail rarely reproduces with its parental species and is a unique mixture of the two in both its outward traits and inward genetic makeup.
The research, published today in the journal PLoS Genetics, is funded by the National Science Foundation (NSF) and the National Institutes of Health.
"Understanding species formation is central to explaining the vast diversity of life on Earth," says Sam Scheiner, program director in NSF's Division of Environmental Biology.
"But we are just beginning to understand the process," says Scheiner. "These researchers made use of an unusual hybrid to unlock knowledge of the genetic basis of species formation."
How new species form is one of the central questions in evolutionary biology, says biologist Krushnamegh Kunte of Harvard University, lead author of the paper.
"Hybrid speciation is more common in plants, but there are very few cases in animals," says Kunte. "This study may create the fullest picture we have to date of hybrid speciation occurring in an animal."
"This is a remarkable demonstration of how hybridization can create populations with a new combination of life history and morphological traits, allowing colonization of novel environments by a 'mosaic genome,'" says biologist Larry Gilbert of the University of Texas at Austin, a co-author of the paper.
"Importantly," he says, "it demonstrates one way that new species can form."
Kunte and colleagues studie
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National Science Foundation