Parasites prevent ants from protecting coffee plants

August 05, 2003

ANN ARBOR, Mich.---Azteca ants are voracious predators that live on coffee plants and aggressively defend their territories. That's generally good for the coffee plants, which are protected in the process against all sorts of insect pests.

But the whole system goes awry when parasitic flies called phorids enter the picture. When they get the chance, the flies lay eggs in Azteca ants' heads, but they also influence the ants' behavior, with far-reaching results, a University of Michigan graduate student has discovered.

"When phorid flies appear near an ant nest, the ants all run back inside the nest, severely limiting their ability to search for or attack their prey," said Stacy Philpott, who will present her findings Aug. 5 at the annual meeting of the Ecological Society of America. "The result in itself is surprising since most people think of a parasite as something that kills its host, not as something that has an effect by changing the behavior of its host."

In experiments conducted on coffee plantations in Mexico, Philpott found that Azteca ants are more efficient predators than other ants, finding and eliminating caterpillars and other potential pests from coffee plants faster than other common ants in the same farms. But when she compared ant attacks on caterpillars on coffee plants where phorids were found with those on phorid-free plants, she found that the numbers of ants patrolling the plants were cut in half when phorids were present. In addition, ants took more than twice as long to carry away caterpillars on plants with phorids, and some caterpillars on those plants escaped ant attacks altogether.

The system illustrates what ecologists call a trophic cascade, in which changes higher up in the food chain cascade or trickle down to affect organisms at lower levels.

"Having phorids in the system cascades down to affect Azteca prey via their interactions with Azteca ants," Philpott said. "The phorids, however, may also affect how Azteca interact with other species of ants or with other predators such as spiders, with potentially more widespread effects in coffee agroecosystems."

It's also possible that birds and other predators on insect pests compensate for the Azteca ants' reduced activity, said Philpott, who plans to investigate the system further. "The overall impacts on coffee production will depend on the interactions among all these groups of predators."

University of Michigan

Related Behavior Articles from Brightsurf:

Variety in the migratory behavior of blackcaps
The birds have variable migration strategies.

Fishing for a theory of emergent behavior
Researchers at the University of Tsukuba quantified the collective action of small schools of fish using information theory.

How synaptic changes translate to behavior changes
Learning changes behavior by altering many connections between brain cells in a variety of ways all at the same time, according to a study of sea slugs recently published in JNeurosci.

I won't have what he's having: The brain and socially motivated behavior
Monkeys devalue rewards when they anticipate that another monkey will get them instead.

Unlocking animal behavior through motion
Using physics to study different types of animal motion, such as burrowing worms or flying flocks, can reveal how animals behave in different settings.

AI to help monitor behavior
Algorithms based on artificial intelligence do better at supporting educational and clinical decision-making, according to a new study.

Increasing opportunities for sustainable behavior
To mitigate climate change and safeguard ecosystems, we need to make drastic changes in our consumption and transport behaviors.

Predicting a protein's behavior from its appearance
Researchers at EPFL have developed a new way to predict a protein's interactions with other proteins and biomolecules, and its biochemical activity, merely by observing its surface.

Spirituality affects the behavior of mortgagers
According to Olga Miroshnichenko, a Sc.D in Economics, and a Professor at the Department of Economics and Finance, Tyumen State University, morals affect the thinking of mortgage payers and help them avoid past due payments.

Asking if behavior can be changed on climate crisis
One of the more complex problems facing social psychologists today is whether any intervention can move people to change their behavior about climate change and protecting the environment for the sake of future generations.

Read More: Behavior News and Behavior Current Events 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