Featured Research

from universities, journals, and other organizations

Seed dispersal in Mauritius: Dead as a dodo?

Date:
May 9, 2008
Source:
Public Library of Science
Summary:
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 colonization 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 realize how many interactions have been lost as a result.

"Aldabra tortoise" -- a giant Aldabran tortoise, Aldabrachelys gigantea, feeding on a palm fruit at La Vanille Tortoise Park in Mauritius. These tortoises are potentially the conservation workers of the future in Mauritius and other islands in the Western Indian Ocean, replacing extinct endemic giant tortoises and other extinct frugivores and herbivores.
Credit: Dennis Hansen

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.

Related Articles


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.

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.


Story Source:

The above story is based on materials provided by Public Library of Science. Note: Materials may be edited for content and length.


Journal Reference:

  1. Dennis M. Hansen, Christopher N. Kaiser, Christine B. Müller, Jerome Chave. Seed Dispersal and Establishment of Endangered Plants on Oceanic Islands: The Janzen-Connell Model, and the Use of Ecological Analogues. PLoS ONE, 2008; 3 (5): e2111 DOI: 10.1371/journal.pone.0002111

Cite This Page:

Public Library of Science. "Seed dispersal in Mauritius: Dead as a dodo?." ScienceDaily. ScienceDaily, 9 May 2008. <www.sciencedaily.com/releases/2008/05/080507083958.htm>.
Public Library of Science. (2008, May 9). Seed dispersal in Mauritius: Dead as a dodo?. ScienceDaily. Retrieved March 29, 2015 from www.sciencedaily.com/releases/2008/05/080507083958.htm
Public Library of Science. "Seed dispersal in Mauritius: Dead as a dodo?." ScienceDaily. www.sciencedaily.com/releases/2008/05/080507083958.htm (accessed March 29, 2015).

Share This


More From ScienceDaily



More Plants & Animals News

Sunday, March 29, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Vietnam Rice Boom Piles Pressure on Farmers and the Environment

Vietnam Rice Boom Piles Pressure on Farmers and the Environment

AFP (Mar. 29, 2015) — Vietnam&apos;s drive to become the world&apos;s leading rice exporter is pushing farmers in the fertile Mekong Delta to the brink, say experts, with mounting costs to the environment. Duration: 02:35 Video provided by AFP
Powered by NewsLook.com
Raw: Lioness Has Rare Five-Cub Litter

Raw: Lioness Has Rare Five-Cub Litter

AP (Mar. 27, 2015) — A lioness in Pakistan has given birth to five cubs, twice the usual size of a litter. Queen gave birth to two other cubs just nine months ago. (March 27) Video provided by AP
Powered by NewsLook.com
Jockey Motion Tracking Reveals Racing Prowess

Jockey Motion Tracking Reveals Racing Prowess

Reuters - Innovations Video Online (Mar. 26, 2015) — Using motion tracking technology, researchers from the Royal Veterinary College (RVC) are trying to establish an optimum horse riding style to train junior jockeys, as well as enhance safety, health and well-being of both racehorses and jockeys. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Bear Cubs Tumble for the Media

Bear Cubs Tumble for the Media

Reuters - Light News Video Online (Mar. 26, 2015) — Two Andean bear cubs are unveiled at the U.S. National Zoo in Washington, D.C. Alicia Powell reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins