Alumna, professor pen study on spiders
A new study in the journal Ecological Entomology by Loriann Garcia ’10 and Dr. John Styrsky, associate professor of biology, shows that Eustala spiders stay really still — even with ants crawling all over them.
Their work was also featured in a blog by James D.J. Gilbert, an evolutionary biologist in Australia who writes about “Tiny Monsters.” Scroll down to the section on “The old Jurassic Park Trick” to read about Loriann and Dr. Styrsky’s work.
Their research has also been featured in Science News for Students.
The pair conducted their research in Panama’s Soberani National Park in 2008 and 2009 to understand 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, Dr. Styrsky, 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?
“The biology of the Neotropics is vastly understudied and tropical habitats are 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 species infiltrate and exploit mutualisms and under whether or not exploiter species destabilize mutualisms. Dr. Styrsky said species interactions such as predation and competition have been studied much longer and more in-depth than mutualisms, historically, because mutualisms simply weren’t considered that important.
“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. What the spiders gain from living among the dangerous ants is protection from being eaten by predators such as anoles and birds.