Bell Museum researchers join a worldwide effort to map the tree of life

The Genealogy of Earth

by Jennifer Amie

One of the most amazing tenets of modern biology is the idea that all of life forms on earth—from the tiniest bacteria in the soil to the largest whales in the ocean, from birds in the sky to humans in their skyscrapers—are related. All share a single common ancestor: a single-celled organism that lived billions of years ago and gave rise to all the living (and extinct) creatures of our planet. Because all life on earth is linked on a vast family tree, mapping the roots, branches, and twigs of this tree is one of the most basic—and important—tasks of scientists today.

The National Science Foundation’s Assembling the Tree of Life project supports this work by funding biologists, geneticists, and computer experts around the world in an ambitious 15-year effort to determine the earth’s genealogy. To date, NSF has provided more than $1.5 million to Bell Museum researchers who are doing their part to help piece together a picture first suggested by Charles Darwin more than 100 years ago.

Bell Museum scientists are working on the bird, fungi, fish, and insect branches of the tree of life. The most recent grant was received by curator of Lepidoptera Susan Weller and her colleagues at the University of Maryland to work on major divisions within Lepidoptera (moths and butterflies). Weller’s role is to coordinate an international network of 30 scientists who specialize in Lepidopteran anatomy and DNA. Her own speciality is mapping the relationships among the Noctuoideae. This superfamily of 55,000 species comprises gypsy moths, tiger moths, cutworms, vampire moths, and prominent moths.

Lepidoptera are the largest single group of plant-feeding insects, with more than 160,000 species, and are a vital part of terrestrial ecosystems as pollinators, food for vertebrates, and nutrient recyclers (their droppings enrich soil). They are also one of the most damaging groups of agricultural pests. Understanding their lineage will not only have practical applications for agriculture, but also will shed light on a fascinating aspect of natural history: the evolutionary diversification of the Lepidoptera in association with the rise of flowering plants which began in the age of the dinosaurs.

The work of Weller and her colleagues links the best of traditional biology with the latest in online innovations. Before the advent of DNA analysis, scientists classified organisms exclusively according to their morphology, or anatomical traits. Moths, for example, are identified by their distinctive wing patterns, caterpillars (hairy, smooth, spiny, etc), hearing organs, and genitalia. The problem with this, says Weller, is that there is no Gray’s Anatomy for moths and butterflies.

“Scientists may be using different terms for the same anatomical structure,” she says. The lack of a shared vocabulary inhibits a process that’s at the heart of the scientific method: the ability of one researcher to repeat another’s work and compare results. “How do you repeat someone’s results if you’re not looking at the same thing?” asks Weller. “We need an illustrated glossary of terms for Lepidoptera to ensure that we’re all on the same page.” That’s just what they’re going to create online, developing a type of Web site (known as a “wiki”) that is authored collaboratively. The site will be similar to Wikipedia, a groundbreaking online encyclopedia that is written and edited by users and is constantly expanding based on the input of its online community. In the same way, the scientists’ Lepnet AToL online encyclopedia of butterfly and moth anatomical terms will grow as researchers around the world add and edit anatomical information that will help determine relationships among species. The Web site will also be available to the public. “You can watch us build this over the next five years,” says Weller.

DNA analysis also plays a role in the Lepnet project. Weller and her colleagues will generate and analyze DNA sequence data to map an evolutionary tree describing the relationships of the major superfamilies of moths and butterflies.

“We still have major challenges in finding and describing all biological diversity,” says Weller. “That’s why the Assembling the Tree of Life project is so important. It gives an infusion of talent working on the problem. Eventually scientists working on all the little pieces and parts will plug into the main branches, and those will be plugged into the trunk, giving us a fuller picture of life on earth.”

The 1.7 million species known to science today are believed to make up at most 10 percent of the total species that exist on the planet. To establish a truly comprehensive tree of life, scientists must also document the other 90 percent—a task made especially difficult when species are disappearing at an ever-increasing rate. Mapping the tree of life is, in part, a race against time as scientists try to identify species before they are lost forever. In some cases, says museum director Scott Lanyon, also a recipient of the NSF grants, knowing how species are inter-related can help conservationists decide which species to save, given limited resources. “The overall goal is to preserve as much genetic diversity as possible,” says Lanyon, “and to do that, we need to know how things are related.”

Lanyon, an ornithologist, is part of a group of scientists assembling the branch of the tree that includes dinosaurs and modern birds. He’s focusing on blackbirds, tanagers, warblers, cardinals, and sparrows, a group that makes up approximately 10 percent of the world’s birds. Because the group is so well-studied, says Lanyon, “We’re going to have one of the best known branches.” (In fairness to Weller, there are as many species of tiger moths alone as there are species of birds. Because insects vastly outnumber birds—3 million insect species versus approximately 9,000 bird species—entomologists have their work cut out for them.)

Ultimately, says Lanyon, the tree of life will provide critical context for all biological research. “Every species on this planet is the result of evolution and continues to evolve today,” he says. The tree of life describes this evolutionary history. With more than a decade of research and global collaboration ahead, the project—like Weller’s wikipedia—will continue to expand. It’s an epic effort that matters so much to scientists, says Lanyon, for the most basic of reasons. “We are the only planet we’re aware of on which life has evolved. The tree of life will tell us where we came from.”