The Species Tricorder – Two Years Later
Two years ago I traveled to Costa Rica and met two amazing scientists: Daniel Janzen and Willie Hallwachs. Janzen and Hallwachs and their many colleagues – professional scientists, students, and an important group of “parataxonomist” collectors – work the Area de Conservación de Guanacaste, where they catalog and study the organisms that live there, while trying to protect and expand the park.
A few weeks later I went to Ontario to meet Paul Hebert, a geneticist at the University of Guelph and the inventor of a novel method for identifying species using very short snippets of DNA. Hebert was using material – moths and wasps, mainly – collected in Guanacaste to prove that his idea was valid.
When I wrote about it, this method was highly controversial. Could you really take part of the job of the expert taxonomist – the identification of species – and routinize it, reduce the cost, and provide identifications of even very hard to tell apart animals as a kind of standard technical service? Or, as Dan Janzen liked to ask: could we build a species tricorder?
A couple of months ago I found out that my story, A Simple Plan to ID Every Creature on Earth, is going to be awarded the 2009 AAAS Kavli Science Journalism Award for the best science story published in a magazine during the preceding year. I’m very proud of this award, and grateful to Dan, Winnie, Paul, and their colleagues for having been willing to answer endless questions about their work. Critics of barcoding – also eminent scientists, including the Director of the Jepson Herbarium Brent Mishler - were equally open and helpful.
I took many photos on my trip, and I thought I would post a few of them along with some updated barcoding material before I head down to San Diego for the AAAS meeting.
Here is a photo of Dan at his desk. Below it is the description of him working that opened my piece for Wired.
The utopian lepidopterist holds a pin in each hand. His style is ambidextrous and probably unique. He catches two forewings of a dead moth simultaneously and pins them to his drying board, and then, in a continuous sweep, he does the same with the hind wings. He repeats these motions again and again, like a conductor with tiny batons. Outside, it is hot and bright. Inside, it is hot and dark. The lepidopterist, whose name is Dan Janzen, has been working here in this Costa Rican forest for more than 40 years. He is married to his research partner, Winnie Hallwachs, and the two of them occupy a small house with a roof of corrugated metal whose eaves cast deep shade. During the day they work under artificial light. At night bats flit through the gaps at the top of the wall, do hairpin turns in the air, and exit again without slowing. The utopian lepidopterist’s aim is to put names on all the moths and butterflies in the forest. He wants to know more than just the names, of course; he wants to know who lives where and who eats whom and to unravel the mysteries of the ecosystem. But his first question is always the most basic one. This moth, here on the drying board: What is it called?
Here is one of the rearing stations Janzen and his colleagues operate. Each bag contains a caterpillar and some of the leaves of the plant it was found on.
[The area is...] strung with ropes. Beneath the ropes hang hundreds of plastic bags full of leaves, and inside every bag there is a caterpillar, a pupa, a moth, or some flies or wasps that have managed to parasitize the caterpillar, eat the pupa, and emerge into the middle of this scientific experiment. Like the insects in the neighboring bags, the destiny of these parasites is to be frozen, dried, identified, barcoded, and shipped to a museum for reference. Here, and in 10 other caterpillar-rearing stations in the forest, Janzen, Hallwachs, and their many local collaborators have solved taxonomic mysteries that go back hundreds of years. “Some of these moths have had names forever, and their caterpillars, too, and they’ve never been recognized as the same species,” Janzen says.
Janzen is 71. I enjoyed grabbing this picture of him on the road the rearing station.
There was electricity available at the rearing station, so I got to sit outside and catch up on my notes….
What has happened after the story appeared? Was the controversy resolved? Over the last two years, the advocates of barcoding appear to have won the day. I keep up with ongoing news via Mark Stoeckle’s detailed posts on The Barcoding Life Blog. Recently, reported on a project to use barcoding to determine the species of fly larvae that are important in forensics; although the larvae which feed on corpses can be telling evidence of the time of death, figuring out what species you have can be hard when all you can see is a tiny wriggling worm, with virtually no distinguishing features.
Barcoding also made news recently in Science, with a report by Elizabeth Pennisi on the recent completion of a barcoding analysis of a collection of more than 2500 parasitoid wasps. (The image below is from Dan and Winnie’s collection of material, it shows the actual wasp larvae (Euplectrus walteri) emerging from the caterpillar – yum!)
Pennisi, in her story, The Little Wasp That Could, (full text behind a subscription wall, unfortunately) gives an excellent description of why figuring out what wasp you have on your hands is interesting, important, and – before barcoding – very hard:
The British geneticist J. B. S. Haldane once famously quipped that God seems to have had an inordinate fondness for beetles, given their numbers and diversity. If so, then he must have been besotted by parasitoid wasps. Tinkerbells of the animal kingdom, many of these insects are no bigger than fleas, yet they may well outnumber beetles.
Unlike beetles, however, parasitoid wasps aren’t exactly charismatic. “You get one in your eye and pull it out with your finger and think it’s a piece of dust,” says Daniel Janzen, an ecologist at the University of Pennsylvania. “There’s millions of individuals out there, and you don’t even know they exist.” Yet these inconspicuous insects play a crucial role in natural ecosystems and in agriculture. They destroy the eggs, larvae, or cocoons of countless species of insects and arthropods, sometimes with hugely beneficial effects: The U.S. Department of Agriculture (USDA) estimates that parasitic wasps save the United States at least $20 billion annually by controlling invasive species. “I think very few people realize what a force they are in the biology of our planet,” says Michael Strand, an entomologist at the University of Georgia, Athens.
A 2008 DNA bar-coding analysis of 2597 parasitoid wasps from his collection turned up 313 species, not the 171 researchers had previously thought. M. Alex Smith of the University of Guelph in Canada and Josephine Rodriguez of UC Santa Barbara discovered that what was believed to be a single species—a 2-millimeter-long wasp called Apanteles leucostigmus with a black body and a white rhomboid patch on its wing—proved to be 36. And there were many more examples of previously unrecognized species, Janzen, Rodriguez, Smith, and their colleagues reported in the 26 August 2008 issue of the Proceedings of the National Academy of Sciences.
Alex Smith, mentioned in the above passage, was on one of the trips I made to Costa Rica. I enjoyed his company tremendously. Here is a picture of him with a beetle on his head. He did not put it there. We were collecting moths at night, and just saw a nice spot and decided to land.
Finally, here a couple of good videos that capture some of the interesting stuff going on in this line of work. The first is a short video about parasitoid wasps; it is very well explained and there are a few great images.
But this one, a Google talk by Dan Janzen and Paul Hebert, is more informative and inspirational. Here Janzen and Hebert lay out the whole picture of what it would mean to be able to identify species on the planet, and how we could get there.
There is an excellent collection of links here, at the Ontario Genomics Institute, with more information about the relationship between DNA barcoding, species identification, and environmental conservation.