An international team of lepidopterists has compiled the most comprehensive evolutionary tree for butterflies to date. The results appear in the journal Current Biology.
Dr. Akito Kawahara, a researcher with the Florida Museum of Natural History’s McGuire Center for Lepidoptera and Biodiversity on the University of Florida campus, and co-authors produced a butterfly evolutionary tree with a 35-fold increase in genetic data and three times as many taxa as previous studies.“We still have a long way to go, but this is the first comprehensive map of butterfly evolution,” Dr. Kawahara said.“Lots of previous studies cover butterfly evolution on smaller scales — by locality or taxon — but surprisingly few have reached across the breadth of butterfly diversity.”The researchers analyzed a dataset of 352 genetic markers from 207 butterfly species representing 98% of tribes, which are a rank above genus but below family and subfamily.Their findings paint a detailed picture of relationships between butterflies and point to some name changes.The data confirm that swallowtails are a sister group to all other butterflies, meaning they were the first family on the butterfly family tree to branch off.But while previous literature groups swallowtails, birdwings, zebra swallowtails and swordtails together, this study shows they do not share a common ancestor, a finding supported by the fact that these butterflies feed on different host plants.“That tells us that butterflies and plants may have evolved together,” Dr. Kawahara said.A finding that surprised the team is that the blues are nested within the hairstreaks.“Both of these groups have remained quite stable through time, but our study shows that a substantial rearrangement of the classification is necessary,” said lead author Dr. Marianne Espeland, who started the project as a postdoctoral researcher at the Florida Museum and is now curator and head of the Lepidoptera section at the Zoological Research Museum Alexander Koenig in Germany.Most blues and hairstreaks and some metalmarks have mutually beneficial relationships with ants: butterfly larvae provide sugary nectar in exchange for the ants’ protection from predators.The scientists found this association evolved once in blues and hairstreaks and twice in metalmarks.Previous studies suggest the first butterflies date back more than 100 million years, a date this study supports.But most of the lineages that exist today originated after the mass extinction event that killed off non-avian dinosaurs about 65 million years ago.“It is actually quite nice that the ages inferred in this study are relatively similar to those found in previous studies since this means that we are gradually converging towards a consensus, which should be close to the correct ages,” Dr. Espeland said.“One curious finding is that the phylogeny suggests butterfly-moths — the only butterflies known to be nocturnal — developed hearing organs before bats, their primary predator, appeared,” Dr. Kawahara said.“I’m fascinated by the timing of when these hearing organs developed and why. There’s a lot of mystery and uncertainty here.”