Featured Research

from universities, journals, and other organizations

More wolf spiders feasting on American toads due to invasive grass, study shows

Date:
August 27, 2014
Source:
University of Georgia
Summary:
An invasive grass species frequently found in forests has created a thriving habitat for wolf spiders, who then feed on American toads, a new study has found. Japanese stiltgrass, which was accidentally introduced to the US in the early 1900s, is one of the most pervasive invasive species. Typically found along roads and in forests, it has been found to impact native plant species, invertebrate populations and soil nutrients.

UGA researchers found that Japanese stiltgrass affects arachnid predators. Wolf spiders, like the one above, thrive in the grass. As their numbers grow, more spiders then feed on young American toads, ultimately reducing the amphibian's survival wherever this grass grows.
Credit: Jayna DeVore/UGA

An invasive grass species frequently found in forests has created a thriving habitat for wolf spiders, who then feed on American toads, a new University of Georgia study has found.

Related Articles


Japanese stiltgrass, which was accidentally introduced to the U.S. in the early 1900s, is one of the most pervasive invasive species and has spread to more than a dozen states in the past century, particularly in the Southeast. Typically found along roads and in forests, it can survive in widely diverse ecosystems and has been found to impact native plant species, invertebrate populations and soil nutrients.

In a new study recently published in the journal Ecology, UGA researchers found that Japanese stiltgrass also is affecting arachnid predators: Lycosid spiders, commonly known as wolf spiders, thrive in the grass. As their numbers grow, more spiders then feed on young American toads, ultimately reducing the amphibian's survival wherever this grass grows.

John Maerz, an associate professor in UGA's Warnell School of Forestry and Natural Resources and one of the paper's authors, said they found the grass had the greatest negative impact on toad survival in forests where toad survival was naturally high.

"In other words, the grass is degrading the best forests for young toad survival," Maerz said. "Another important finding was that the invasive grass affects toads by changing interactions among native species rather than the grass having a direct effect on the native toads."

Jayna DeVore, who led the project while earning her doctorate in the Warnell School, said people often don't fully realize how much structural changes in an environment can affect how animals interact.

"Ecosystems are so incredibly complex that it can be surprisingly difficult to foresee just how environmental changes, such as an invasion, will affect organisms living in affected areas," said DeVore, who is now a postdoctoral fellow with the University of Sydney in Australia. "I think that one of the unique things about this study is that it not only documents the fact that this plant invasion reduces the survival of a native species, but also determines the mechanism through which that occurs."

Maerz has been interested in the effects of Japanese stiltgrass on forest ecosystems for years. When DeVore and Maerz originally found lower survival of American toads at eight locations in Georgia where stiltgrass is actively invading, they initially speculated that the grass was reducing the toads' food supply by reducing insect populations -- few native insects eat the Asian grass. However, after noticing the wolf spiders routinely preying upon toads in invaded habitats, it began to click, Maerz said.

Spiders are incredible predators, he explained, and they eat everything -- even other spiders. That typically keeps spider populations in check, Maerz said, but Japanese stiltgrass is "kind of like a tall shag carpet," and it provides the cannibalistic spiders refuge from one another. The accumulation of large, predatory spiders in these invaded habitats then results in higher mortality for small toads that have recently emerged from wetlands.

To test their hypothesis, DeVore and Maerz created cages where they could control the presence of stiltgrass and spiders. They found that spider densities were 33 percent higher and toad survival decreased by 65 percent in cages with the presence of stiltgrass. The presence of stiltgrass alone, in the absence of spiders, did not affect toad survival.

"Spiders are actually tremendously important and incredibly abundant predators on the forest floor, and they will eat many of the small species that live there, so this effect is unlikely to only influence toads," DeVore said. "And there are also other ways in which invasion by this Asian plant may influence species on the forest floor. We documented changes in invertebrate densities and soil characteristics that may affect other species that depend on these invertebrates for prey or are sensitive to changes in soil properties such as moisture and pH."

DeVore and Maerz are trying to determine whether the grass invasion is affecting other amphibian species in similar or predictable ways. It's "logistically impossible" to test the effects on an environmental change on every species that could be impacted, DeVore said, and even related species often react dramatically differently. The researchers hope to show that by accounting for certain aspects of the behavior and biology of a species, it will allow them to predict how they react.

The paper by DeVore and Maerz was featured on the cover of the July issue of Ecology.


Story Source:

The above story is based on materials provided by University of Georgia. The original article was written by Sandi Martin. Note: Materials may be edited for content and length.


Journal Reference:

  1. Jayna L. DeVore, John C. Maerz. Grass invasion increases top-down pressure on an amphibian via structurally mediated effects on an intraguild predator. Ecology, 2014; 95 (7): 1724 DOI: 10.1890/13-1715.1

Cite This Page:

University of Georgia. "More wolf spiders feasting on American toads due to invasive grass, study shows." ScienceDaily. ScienceDaily, 27 August 2014. <www.sciencedaily.com/releases/2014/08/140827131805.htm>.
University of Georgia. (2014, August 27). More wolf spiders feasting on American toads due to invasive grass, study shows. ScienceDaily. Retrieved November 27, 2014 from www.sciencedaily.com/releases/2014/08/140827131805.htm
University of Georgia. "More wolf spiders feasting on American toads due to invasive grass, study shows." ScienceDaily. www.sciencedaily.com/releases/2014/08/140827131805.htm (accessed November 27, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Thursday, November 27, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Classic Hollywood Memorabilia Goes Under the Hammer

Classic Hollywood Memorabilia Goes Under the Hammer

Reuters - Entertainment Video Online (Nov. 26, 2014) The iconic piano from "Casablanca" and the Cowardly Lion suit from "The Wizard of Oz" fetch millions at auction. Sara Hemrajani reports. Video provided by Reuters
Powered by NewsLook.com
Pet Dogs to Be Used in Anti-Ageing Trial

Pet Dogs to Be Used in Anti-Ageing Trial

Reuters - Innovations Video Online (Nov. 26, 2014) Researchers in the United States are preparing to discover whether a drug commonly used in human organ transplants can extend the lifespan and health quality of pet dogs. Video provided by Reuters
Powered by NewsLook.com
From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

Newsy (Nov. 25, 2014) The US FDA is announcing new calorie rules on Tuesday that will require everywhere from theaters to vending machines to include calorie counts. Video provided by Newsy
Powered by NewsLook.com
Feast Your Eyes: Lamb Chop Sent Into Space from UK

Feast Your Eyes: Lamb Chop Sent Into Space from UK

Reuters - Light News Video Online (Nov. 25, 2014) Take a stab at this -- stunt video shows a lamb chop's journey from an east London restaurant over 30 kilometers into space. Rough Cut (no reporter narration). 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