Researchers find invasive species are healthy species -- They leave their parasites behind

February 05, 2003

(Santa Barbara, Calif.) -- Globalization of commerce, especially by ships and air traffic, transports hitchhiking plants and animals around the world and in many cases they become pests in the new location -- according to an article in the February 6 issue of the journal Nature. One advantage that could explain their success is that the invaders often arrive without the parasites that hold them in check at home.

First author Mark E. Torchin, assistant research biologist at the University of California, Santa Barbara, said that the team of authors analyzed 26 invading animal species -- mollusks, crustaceans, fishes, birds, mammals, amphibians and reptiles -- chosen randomly, and found that, in general, the introduced populations had only half as many parasites as native populations.

"On average, an animal has 16 parasites at home, but brings less than three of these to new areas that it invades," said Torchin. "In the new region, parasites are not well matched to novel hosts, and only about four parasites will successfully attack an invading species."

On this research Torchin teamed up with co-authors Kevin Lafferty, an assistant adjunct professor of biology at UCSB and a marine ecologist with U.S. Geological Survey; Armand Kuris, professor of biology at UCSB; his graduate student, Valerie McKenzie; and Andrew Dobson, professor in the department of ecology and evolutionary biology at Princeton University.

Kuris explained that parasites are so pervasive that parasitism is the most common lifestyle on Earth. Many parasites don't just make animals sick -- they may castrate them, change their behavior, or even kill them. By leaving parasites behind, introduced species have a strong advantage over less fit native competitors which remain fettered by their own full complement of parasites.

Borrowing from popular culture, Lafferty said, "Parasites are to invasive species what kryptonite is to Superman. On his home planet Krypton, kryptonite was a regulator, keeping Superman ordinary. Freed from kryptonite on Earth he gained super powers. But unlike Superman who used his power for good deeds, invasive species can be devastating."

The European green crab (Carcinus maenas) is one voracious predator that has been studied extensively by the authors Torchin, Lafferty and Kuris. It has had a devastating effect on East Coast fisheries and is now threatening fisheries in the Northwest as it moves from California toward Puget Sound in Washington. The green crab eats Dungeness crabs, rock crabs, mussels, oysters and clams. In northern New England, the advent of the green crabs has been associated with the demise of the softshell clam fishery. On the West Coast, the oyster, mussel and clam mariculture industries are threatened, as are Dungeness and rock crab fisheries, and bait fisheries. The green crab has also invaded Australia, Japan, Tasmania and South Africa.

Torchin, Lafferty and Kuris found that in Europe, the green crab's native home, parasitic barnacles castrated the crabs. Where the barnacles were common, the crabs were small and rare. Conversely, the scientists found that crabs were big and abundant in areas where barnacles were uncommon.

In a separate, but parallel, study also published in Nature, Charles Mitchell and Alison Power of Cornell University found that introduced plants most likely to become weeds are those that have left behind the most pathogens. The plant and animal groups worked side by side on the research at UCSB's National Center for Ecological Analysis and Synthesis.

According to both groups of authors, bringing in parasites from a pest's native range can hinder superpests. The benefits to this organic form of pest control are sustainability, low cost and reduced dependence on pesticides. But the researchers cautioned that biological control of pests is risky if the parasites are not specific to the target pest.

"Suitable biocontrol agents should be harmless to native species, just as kryptonite is harmless to Earthlings," said Lafferty.
-end-


University of California - Santa Barbara

Related Invasive Species Articles from Brightsurf:

The invasive species that Europe needs to erradicate most urgently are identified
An international research team analyzed the risk impact and the effectiveness of possible erradication strategies for invasive species already in the region as well as those that have yet to arrive

Crayfish 'trapping' fails to control invasive species
Despite being championed by a host of celebrity chefs, crayfish 'trapping' is not helping to control invasive American signal crayfish, according to new research by UCL and King's College London.

Climate change is impacting the spread of invasive animal species
What factors influence the spread of invasive animal species in our oceans?

Invasive alien species may soon cause dramatic global biodiversity loss
An increase of 20 to 30 per cent of invasive non-native (alien) species would lead to dramatic future biodiversity loss worldwide.

Protected areas worldwide at risk of invasive species
Protected areas across the globe are effectively keeping invasive animals at bay, but the large majority of them are at risk of invasions, finds a involving UCL and led by the Chinese Academy of Science, in a study published in Nature Communications.

Charismatic invasive species have an easier time settling into new habitats
An international study, in which the University of Cordoba participated, assessed the influence of charisma in the handling of invasive species and concluded that the perception people have of them can hinder our control over these species and condition their spread

Invasive species with charisma have it easier
It's the outside that counts: Their charisma has an impact on the introduction and image of alien species and can even hinder their control.

Invasive species that threaten biodiversity on the Antarctic Peninsula are identified
Mediterranean mussels, seaweed and some species of land plants and invertebrates are among the 13 species that are most likely to damage the ecosystems on the Antarctic Peninsula.

Research networks can help BRICS countries combat invasive species
BRICS countries need more networks of researchers dedicated to invasion science if they wish to curb the spread of invasive species within and outside of their borders.

Look out, invasive species: The robots are coming
Researchers published the first experiments to gauge whether biomimetic robotic fish can induce fear-related changes in mosquitofish, aiming to discover whether the highly invasive species might be controlled without toxicants or trapping methods harmful to wildlife.

Read More: Invasive Species News and Invasive Species Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.