Long-forgotten samples may help save species
The snails, famous since the late 1800s as classic examples of species that had rapidly diversified in an isolated environment, later became victims of a "spectacularly inept attempt at biological control," said U-M mollusk expert Diarmaid Ó Foighil.
The trouble started in 1975 when the predatory rosy wolf snail was deliberately introduced to many South Pacific islands to control an agricultural pest. The problem was, the rosy wolf snail had a bigger appetite for native land snails than for the pests it was supposed to devour. Over the years, the native snails were virtually wiped out, and today only six of the original 61 species of land snails originally found in the Society Island archipelago survive in the wild.
Researchers and conservationists stepped in during the 1980s and began setting up captive populations in European and North American Zoos (eventually including the Detroit Zoo), and snails from these breeding programs gradually are being reintroduced to protected areas in their former ranges. Understanding the evolutionary relationships between the captive populations, the remaining wild snails and the original 61 species would greatly aid conservation and rehabilitation efforts, said Ó Foighil, and that's where those long-forgotten vials come in.
Back in 1970, U-M professor emeritus John B. (Jack) Burch traveled to Tahiti to study the native snails, which had not yet been decimated by the rosy wolf snail. Hiking deep into valleys where the snails were found, Burch collected several thousand specimens. Most were preserved in alcohol for anatomical studies, but he also shipped about 600 live snails back to U-M to be freeze-dried. At the time, researchers used proteins to study relationships among species, and freeze-drying preserves proteins. The plan was for Burch and a collaborator in Hawaii to use the freeze-dried material for a detailed study of evolutionary relationships in the famous Tahitian snails. But the collaborator died before the research could be done, and Burch became absorbed in other projects, leaving the vials of freeze-dried snails in three wooden trays in a freezer at the U-M Museum of Zoology.
If not for a chance conversation with Burch, Ó Foighil, who came to the University in 1995, might never have known about the vials and their conservation potential. "He had told me from time to time that he'd been in Tahiti, and I didn't think too much about it," said Ó Foighil, "but then just about a year ago he mentioned all the stuff in the freezer, and I realized what a valuable resource we have. We have at hand, in freeze-dried form, a comprehensive sampling of the Tahitian land snail fauna from a point in time five years prior to the devastating introduction of the rosy wolf snail."
By extracting, amplifying and analyzing DNA from the samples, as well as from snails that die naturally in the zoo collections, Ó Foighil and colleagues can construct evolutionary trees. Some of the information they'll obtain will be mainly of academic interestsettling such questions as whether the snails diversified into separate species before or after arriving in Tahiti from neighboring islandsbut some will have practical uses. For example, the information may help conservationists figure out which captive snail populations are best to reintroduce to the wild and which of the remaining wild populations they should focus future conservation efforts on.
"The story here, in terms of conservation biology, is a horror story, but it's not all black because some of these snails can be saved," said Ó Foighil, an associate professor of ecology and evolutionary biology and a curator at the museum. "And by being able to reference what's saved with the original fauna, we can have a rational conservation process."
The newfound uses for the old samples also underscore the value of museum collections and fundamental science, Ó Foighil added. "When Jack Burch sampled these snails, he didn't know they were going to go extinct. It's a classic case of the unexpected utility of such basic, collection-oriented research."
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Contact: Nancy Ross-Flanigan