Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Not just the birds

08.02.2006


Introduced foxes throw a wrench in the food web



Indirect effects of predators

In an extensive study, researchers from the University of Montana, University of California - Santa Cruz, and the University of California - Davis have shown that a top predator strongly affected plants and animals at the bottom of an island food web by eating organisms that transport nutrients between ecosystems. "An introduced predator alters Aleutian island plant communities by thwarting nutrient subsidies," is published in the February issue of Ecological Monographs.


As any biologist can attest, cells, organelles, and organisms maintain specific surface to area ratios to ensure life. Similar relations have been observed in regard to an island’s size and nutrient deposition. In many cases, a small island with a large perimeter touching the sea receives more nutrients from marine ecosystems than a large island due to the differences in surface-to-area ratios. In a new study by John Maron, James Estes, Donald Croll, Eric Danner, Sarah Elmendorf, and Stacey Bucklelew, scientists have discovered that the introduction of a top predator has even affected this system.

"Our results show that the ecological effects of fox introductions extended well beyond the direct reductions of bird populations. We have clear evidence that foxes influence the terrestrial plant community and ecosystem dynamics through one particular route," state the researchers in their study.

The experiment

The Aleutian archipelago has over 450 islands in the highly productive North Pacific Ocean and Bering Sea. In the harsh northern climate, the islands are covered in maritime tundra and nutrient-impoverished soil. With no native mammals, vast populations of seabirds (29 species currently) use the area for nesting. However, over the last 100-150 years, the introduction of arctic foxes and Norway rats (Rattus norvegicus) reduced the number of birds nesting on the islands.

Arctic foxes were introduced in the late 1800’s to maintain the North Pacific fur trade, and later removed in an attempt to return the islands to their more natural states. Most of the islands are now fox-free, but the effects of their presence are still visible; birds have been slow to return to the islands to nest.

The region is its own experimental test site. The foxes were introduced to almost a quarter of the islands, about 100 total. The seabirds that inhabited the islands transported nutrients from the nearby seas to the islands via their guano, or excrements. Rich in phosphorous and nitrogen, researchers estimated that guano was reduced by over an order of magnitude on the fox-infested islands.

The reduced nutrient flow affected plants, spiders, other birds, flies, and slugs.

Nutrient status coincided with strong shifts in the structure of plant communities. Upon further experimentation, the researchers found gramanoids -- or grasses -- out-competed the slower growing dwarf shrubs and forbs. The islands with foxes had more dwarf shrubs and forbs, while those with no foxes were dominated by grasses.

Even when researchers took into account differences in island size and distances from shore, the study still showed significant differences between the fox-free and fox-infested islands.

"By disconnecting the nutritional link from sea to land, the introduction of foxes to the Aleutians has reduced or eliminated the significance of the perimeter-to-area relationship that is so clearly evident on fox-free islands," say the authors.

Previous studies have focused on trophic cascades in marine ecosystems, showing that top predators can indirectly alter plant productivity, with varying effects. Most studies on land-based ecosystems have been smaller in scale. These studies have not revealed the large community-wide indirect effects that are often found in aquatic trophic cascades, or have only shown the effects of predators from the top down to lower levels. This study shows an indirect pathway in which a predator affects a food web.

According to the researchers, the results "bolster a growing body of work indicating that island food webs are strongly subsidized by the movement of nutrients from adjacent productive waters onto less productive land."

Annie Drinkard | EurekAlert!
Further information:
http://www.esa.org

More articles from Ecology, The Environment and Conservation:

nachricht How does the loss of species alter ecosystems?
18.05.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

nachricht Excess diesel emissions bring global health & environmental impacts
16.05.2017 | International Institute for Applied Systems Analysis (IIASA)

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: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>