Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Seed dispersal in mauritius -- dead as a dodo?

07.05.2008
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 unique animals. The litany includes the famous flightless dodo, giant tortoises, parrots, pigeons, fruitbats, and giant lizards. It is comparatively easy to notice the los­­s of a species, but much more difficult to realise how many interactions have been lost as a result.

Recent work has highlighted how it is not species diversity per se, which breathes life into ecosystems, but rather the networks of interactions between organisms. Thus, the real ghosts in Mauritius are not as much the extinct animals themselves, but more importantly the extinct networks of interactions between the species.

Reporting in this week’s PLoS ONE, Dennis Hansen, Christopher Kaiser and Christine Müller from the University of Zurich investigate how the loss of seed dispersal interactions in Mauritius may affect the regeneration of endemic plants. Why is it important for seeds to be dispersed away from maternal plants" One possible answer is given by the Janzen-Connell model, one of the most studied ecological patterns in tropical mainland forests –but which so far has not been experimentally investigated on oceanic islands. In essence, the model suggests that for successful seedling establishment, seeds need to be dispersed away from adult trees of the same species, to escape natural enemies that are associated with the adult trees (seed predators, pathogens, herbivores). The recent loss of most frugivores in Mauritius has left many fleshy-fruited plant species stranded without crucial seed dispersal interactions, leaving the na tural regeneration dynamics of the forests at a virtual standstill.

Within the framework of the Janzen-Connell model, the ecologists investigated seed germination and seedling survival patterns of one of the many critically endangered endemic trees, Syzygium mamillatum (Myrtaceae), in relation to distance from maternal trees. The results showed strong negative effects of proximity to maternal trees on growth and survival of seedlings, suggesting that dispersal is crucial for successful seedling establishment of this species. However, no extant frugivores eat the fruits of S. mamillatum, and most fruits are left to rot on the forest floor. In pristine Mauritius, the fruits would likely have been eaten and the seeds dispersed by ground-dwellers such as the dodo, the giant tortoises or giant lizards.

It may seem an impossible task to resurrect these lost interactions – simply because the Mauritian dodo is, well, dead as a dodo. However, recent studies have suggested rejuvenating lost interactions in currently dysfunctional ecosystems by using analogue species to replace extinct species – so-called ‘rewilding’. In one of the first experimental assessments of the use of ecological analogue seed dispersers, the Zurich group of ecologists successfully used giant Aldabran tortoises as stand-ins for the two extinct Mauritian tortoises in feeding experiments. Seedlings from gut-passed seeds grew taller, had more leaves, and suffered less damage from natural enemies than any of the other seedlings. The results thus show that Aldabran giant tortoises can be efficient analogues that can replace extinct endemic seed dispersers of S. mamillatum.

Overall, while it is acknowledged that oceanic islands harbour a disproportionally large fraction of the most critically endangered plant species in the world, the study highlights how little we know about how the predictions of the Janzen-Connell model affects the regeneration and longer-term survival of endangered plants on islands. The results potentially have serious implications for the conservation management of rare plants on oceanic islands. Here, plants are often crammed into very small nature reserves, in which seedlings may be unable to disperse far enough to escape high natural enemy pressures around adult trees.

Lastly, in contrast to recent controversy about rewilding projects in North America and elsewhere, this study also illustrates how Mauritius and other oceanic islands are ideal study systems in which to empirically explore the use of ecological analogue species in restoration ecology.

Dennis Hansen | EurekAlert!
Further information:
http://www.stanford.edu

More articles from Ecology, The Environment and Conservation:

nachricht Upcycling 'fast fashion' to reduce waste and pollution
03.04.2017 | American Chemical Society

nachricht Litter is present throughout the world’s oceans: 1,220 species affected
27.03.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>