Evolution At A Snail's Pace: It's Faster Than You Think

Assistant professor Michael Hellberg of LSU's Department of Biological Sciences and Kaustuv Roy and Deborah Balch of UCSD will have their findings published in the June 1 issue of Science, one of the world's premier scientific journals.

By studying different populations of Acanthinucela spirata, a marine gastropod found throughout the rocky coastal regions of California, the researchers discovered that past climatic changes altered the range of the species, which in turn, caused the species' shell shape to evolve. The scientists believe their findings can be applied to other animals, and that any change in an animal's environment or range, whether caused by climate changes, deforestation or any other means of relocation, could bring about the same results.

Fossil records show that the Earth's most recent series of ice ages pushed the Acanthinucela spirata species from northern California into the southern part of the state, where a number of genetic variations took place within the species. When conditions in the northern part of the state eventually warmed – some 10,000 to 14,000 years ago – some members of the snail species worked their way back in that direction, where they repopulated their old territory. The scientists discovered that the snails in the repopulated area to the north began to evolve differently from their southern counterparts, most noticeably in the shape of their shells. Snails with a thicker, shorter and broader shell emerged. This new shell shape had not previously existed.

The findings may give pause to scientists who plan conservation efforts for endangered species. Many conservation plans for endangered animals include relocating the endangered species away from urban development. However, Hellberg said such a technique could result in evolution of the species, which would, technically, result in the loss of that species as we knew it. "Ranges are pushed around all the time, usually by things like climatic change or real estate development," Hellberg said. "Many conservationists believe that as long as a species can be relocated, it can be saved. But this study shows that the moved species may not continue on unchanged. The fact that it was moved can cause it to change and it won't be the same after all."

Even more interesting is the fact that although the new snails in the northern part of California had a completely new and different look, they were genetically very similar to their relatives in the southern part of the state.

Hellberg pointed out that scientists often use genetic testing to evaluate different species to determine whether they are near extinction or are surviving after being relocated. But the fact that all members of California's Acanthinucela spirata species were genetically similar even though some looked quite different casts doubt on whether genetic testing alone is the best method.

"The real key to our study was the combination of fossil records and genetic tests that we used," Hellberg said. "The genes showed us the history of the snail populations, and the fossils showed us what those populations used to look like. This study helps us to determine the consequences of future range changes by looking at what happened in the past," he said. The study was funded by the National Science Foundation. The scientists decided to work with the Acanthinucela spirata because the species has an excellent fossil record, as do most organisms that reside in shallow ocean water. Hellberg performed all the genetic testing in the study, and Roy and Balch performed the fossil analyses.

"We each had very different techniques," Hellberg said of himself and his colleagues. "And it turned into a very profitable collaboration," he said.