Aggressive ants and sneaky spiders
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| Helen Wolfe (left) and Loriann Garcia search for acacia plants |
A never-before-studied relationship among a Neotropical acacia, ant, and spider captured the attention of an LC biology professor and two undergraduates for eight weeks during the summer of 2008.
Dr. John Styrsky, assistant professor of biology, hopes to continue the work during summer 2011 with help from a student or two.
The ongoing research in Panama's Soberani National Park is aimed at understanding how a type of spider is able to survive on an acacia plant that is aggressively protected by ants with a sting that exceeds that of the fiercest fire ant.
The relationship between the acacia and the ant, in which both species benefit each other, is a classic example of mutualism, said "In return for room and board, the ants are extremely aggressive and patrol the plant," he said. This keeps animals, ranging from insects to deer and other mammals, from eating the acacia.
While doing some bird research in the park several years ago, Dr. Styrsky noticed that there was also a small brown spider that managed to intrude into this symbiotic relationship on a particular species of acacia without apparent consequence. Why did the ants allow the spiders to share their territory, or perhaps it's better to ask how could the spiders escape harm while hanging out among such hostile neighbors?
Loriann Garcia '10 of Germantown, Md., and Helen Wolfe '10 of Sterling, Va., both biology majors, joined Dr. Styrsky in his quest to study this unusual trio. "This is a system nobody's ever investigated before," he said.
So why should anyone care about a tropical plant, an aggressive ant, and an orb-weaving spider? "Biology in the Neotropics is vastly understudied and disappearing at a great rate," Dr. Styrsky said. "We are trying to find out a little about life there before it's gone."
The bigger ecological puzzle is figuring out how mutualisms fit into the larger community and how other species in the community affect mutualisms. Dr. Styrsky said species interactions such as predation and competition have been studied much longer and more in-depth than mutualisms, historically, perhaps because fighting and conquering hold more human appeal than a nice, quiet cooperative lifestyle.
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| A Eustala fuscovittata spider keeps still among the ants |
Maybe, just maybe, humans could learn a little something about peaceful co-existence? Dr. Styrsky isn't going that far. The biologist in him just wants to know why the ants don't run off the spiders and what the spiders are getting out of living in such a dangerous neighborhood.
"We found that the spiders often rested on leaves and branches instead of their webs, but were typically not harassed by the ants," he said. "If the spiders move, however, the ants quickly respond and attack them. The spiders escape by jumping on a silk line, retreating to their webs, or simply outrunning their pursuers."
So as long as the spiders are still, which is what spiders mostly are, the ants ignore them, even walking right over them. It's as if the spiders "hide in plain sight," Dr. Styrsky said.
The research is paid for by a grant from the Jeffress Memorial Trust of Virginia and is conducted in affiliation with the Smithsonian Tropical Research Institute. Dr. Styrsky hopes the work can continue for at least another two years, allowing him to take more students back to continue studying this unique trio.
The experience also provides a chance to see some of the more than 400 species of birds that live in the park, including toucans and parrots, as well as a huge variety of mammals, from sloths and anteaters to small wild dogs and giant weasels. Dr. Styrsky's wife Jennifer, also a field biologist, participated in the research and their 3-year-old son Kai also joined them on the trip. Kai particularly enjoyed watching the howler monkeys and 6-foot-long crocodiles.
The professor and his students will spend much of the year analyzing their findings, writing a paper for publication, and presenting their work at national meetings.
For those who want to know, the scientific names are as follows: the plant - Acacia melanocerus; the ant - Pseudomyrmex satanicus; and the spider - Eustala fuscovittata.
