Field experiments suggest introduced species could play understudy for extinct ones
Missing links in ecosystems disrupted by extinctions could be restored by introducing species that perform the same function, field experiments on a remote island suggest.
But some scientists caution against the controversial process, called “rewilding.”.
Take, for example, Syzygium mammillatum, a critically endangered species of tree that grows between 2.5 and 9 meters tall and is found only on
When the researchers fed S. mammillatum fruit to turkeys, a possible ecological analogue of the dodo, none of the thin-hulled seeds survived passage through the bird’s digestive tract. In similar tests, about 15 percent of the seeds from fruit fed to giant Aldabran tortoises passed through the reptiles unscathed. Neither of the species were native to the island.
Hansen and his colleagues then scattered some of the gut-passed seeds and covered them with a one-centimeter layer of tortoise dung in plots about 20 meters away from adult S. mammillatum trees. The scientists also scattered fruit and bare seeds at sites about one meter from an adult tree and at spots about 25 meters away.
The field tests revealed that S. mammillatum seedlings from gut-passed seeds grew taller, had more leaves and suffered less damage from natural enemies such as insects than other seedlings did. These results indicate that the Aldabran tortoises could replace the now-missing seed dispersers of S. mammillatum, thereby enhancing conservation efforts for the tree, the researchers report in the May 7 PLoS ONE.
Hansen and his colleagues “are certainly doing some very interesting and inspiring research in getting to the nitty-gritty of plant reproductive failure in devastated ecosystems,” says Anthony Cheke, an island ecologist formerly at
Despite the apparent success of the experiments in bolstering the reproduction of S. mammillatum, however, scientists seeking to introduce one species to take the ecological place of one that has died out should proceed with caution, says Douglas J. Levey, an evolutionary ecologist at the