Giant tortoises show rewilding can work

Apr 21, 2011

'Rewilding with taxon substitutes', the intentional introduction of exotic species to fulfil key functions in ecosystems following the loss of recently extinct species, is highly controversial, partly due to a lack of rigorous scientific studies.

In a paper published today in , Christine Griffiths of Bristol's School of Biological Sciences and colleagues present the first empirical evidence that rewilding can work.

Exotic giant Aldabra tortoises, Aldabrachelys gigantea, were introduced to Ile aux Aigrettes, a 25-hectare island off Mauritius, in 2000 to disperse the slow-growing ebony Diospyros egrettarum (Ebenaceae), which once covered the island, but today is critically endangered following intensive logging for firewood that lasted until the early 1980s.

To highlight the extent to which the ebony forest had been decimated, the researchers surveyed and mapped all ebony trees in an island-wide survey in 2007 and located a total of 3,518 adult trees. However, large tracts of the island remained denuded of ebony, particularly in the northern and eastern coastal areas nearest to the mainland where logging was most intense.

There had been no regeneration in these areas even though logging ceased thirty years ago because, with the of the island's native giant tortoises, there were no large fruit-eating animals left to disperse the seeds of these critically-endangered trees.

The introduced Aldabra not only ingested the large fruits and dispersed large numbers of ebony seeds, but the process of passing through a tortoise's gut also improved , leading to the widespread, successful establishment of new ebony seedlings in the heavily logged parts of the island.

Christine Griffiths said: "Our results demonstrate that the introduction of these effective seed dispersers is aiding the recovery of this critically endangered tree whose seeds were previously seed-dispersal limited. Reversible rewilding experiments such as ours are necessary to investigate whether extinct interactions can be restored."

Professor Stephen Harris, co-author of the study, said: "Ecological restoration projects generally involve the plant community, as more often the animal components are extinct. There is, however, increasing evidence that restoration ecologists should be most concerned with the decline of species interactions, rather than species extinctions per se. Species interactions structure ecological communities, and provide essential ecosystem processes and functions such as pollination, seed dispersal and browsing, that are necessary for the self-regulation and persistence of a community."

Explore further: Study shows exception to rule of lifespan for fliers, burrowers and tree dwellers

More information: Christine Jane Griffiths, Dennis Marinus Hansen, Carl Gwynfe Jones, Nicolas Zuël and Stephen Harris, Resurrecting extinct interactions with extant substitutes, Current Biology (2011).

Related Stories

Seed dispersal in mauritius -- dead as a dodo?

May 07, 2008

Walking through the last rainforests on the volcanic island of Mauritius, located some 800 km east of Madagascar, one is surrounded by ghosts. Since human colonisation in the 17th century, the island has lost most of its ...

Climate change threatens many tree species: researchers

Jan 24, 2011

Global warming is already affecting the earth in a variety of ways that demand our attention. Now, research carried out at the Hebrew University of Jerusalem indicates that many tree species might become ...

Neighbors gone, fruits gone, species gone

Mar 19, 2007

Neighbors gone, sex gone, fruits gone, species gone. This is the ultra-short conclusion of the findings in a study by Dennis Hansen, Heine Kiesbüy, and Christine Müller from Zurich University, and Carl Jones ...

Recommended for you

In sex-reversed cave insects, females have the penises

2 hours ago

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

2 hours ago

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

Biologists help solve fungi mysteries

6 hours ago

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

User comments : 0

More news stories

Tiny power plants hold promise for nuclear energy

Small underground nuclear power plants that could be cheaper to build than their behemoth counterparts may herald the future for an energy industry under intense scrutiny since the Fukushima disaster, the ...

Hand out money with my mobile? I think I'm ready

A service is soon to launch in the UK that will enable us to transfer money to other people using just their name and mobile number. Paym is being hailed as a revolution in banking because you can pay peopl ...

Classifying cognitive styles across disciplines

Educators have tried to boost learning by focusing on differences in learning styles. Management consultants tout the impact that different decision-making styles have on productivity. Various fields have ...