butterfly family tree
August 2, 2014

DNA Sequencing Shows Evolutionary History Of Butterflies

April Flowers for redOrbit.com - Your Universe Online

In the first study of its kind to use large-scale, next-generation DNA sequencing, a team of researchers from the University of Florida have traced nearly 3,000 genes to the earliest common ancestor of butterflies and moths. The findings, to be published in the Proceedings of the Royal Society B: Biological Sciences, create an extensive “Tree of Lepidoptera” and build the evolutionary framework for future ecological and genetics insect research.

Several of the study’s findings were surprising, including the discovery that butterflies are more closely related to small moths than to larger ones. This one finding completely changes the previously held ideas of butterfly evolution. The study also increased the number of butterfly species known by identifying that some previously classified moths were actually butterflies.

“This project advances biodiversity research by providing an evolutionary foundation for a very diverse group of insects, with nearly 160,000 described species,” said Akito Kawahara, assistant curator of Lepidoptera at the Florida Museum of Natural History on the UF campus. “With a tree, we can now understand how the majority of butterfly and moth species evolved.”

The study, which took a year to complete, is one of the first of its kind to use massive amounts of genetic data to answer questions about butterflies and moths. Kawahara notes that his team’s analysis illuminated monumental discoveries about the lineage of Lepidoptera that strongly contradict the traditional placement of butterflies in evolutionary history.

Next generation sequencing allows scientists to rapidly process large amounts of DNA. Using this method allowed the team to develop an initial sample of 46 species. These species represent the most biodiverse groups of moths and butterflies. The team was also able to combine 22 new transcriptomes, a set of RNA molecules, with 13 genomes, both of which hold genetic material for organisms, as well as identify 2,696 genes by breaking down the DNA and rebuilding it.

The study’s findings will help future researchers to conclusively pinpoint where butterflies belong in evolutionary history, which according to University of Hawaii Insect Museum entomologist and director David Rubinoff has troubled scientists for a long time.

“This study adds to a growing body of knowledge by bringing new techniques to the table and conclusively demonstrating the evolutionary relationships of the most popular insects on the planet,” Rubinoff said. “The methods are novel and build on previous work. This is clearly the future of deep-level evolutionary research.”

Butterflies and moths have a wispy, almost ethereal, beauty. The nature of their soft-bodied larval stages, however, has created challenges for researchers trying to study them in the fossil record. Jesse Breinholt, postdoctoral researcher at the Florida Museum, said that the current study was designed to add more understanding of the evolutionary history than morphological and fossil records studies have been unable to establish firmly so far.

“The few Lepidoptera fossils we have are from about 15 million years ago,” Breinholt said. “The next step is to create a dated evolutionary history for the group, from the earliest ancestors to present day.”

Prior studies that focused on anatomical features theorized that butterflies are close relatives of large moths. The new data indicates, however, that butterflies are more closely related to small (micro) moths. According to Kawahara, the findings also suggest butterflies are the ancestral group to the tens of thousands of moth species currently on the planet. The researchers also found that the Hedylidae family (American butterfly-moths) are not moths at all, but rather, butterflies.

The genetic tree also provides a baseline for understanding the evolution of diurnal (daytime) activity evolved much earlier than previously thought. Daytime activity is a common butterfly trait, and might have come about as the result of bats spreading across the planet, allowing the butterfly to escape the nocturnal predators.

The team hopes to continue their research by investigating the causes of evolutionary transitions across Lepidoptera. Many lineages remain to be examined, despite the new clarity the genetic tree provides.

“I hope this is a starting point for larger studies that account for the great diversity of Lepidoptera,” Breinholt said.

Butterflies of North America (Kaufman Field Guides)by Jim P. Brock