Biology 219 Invertebrates in the News

“Native Ants Use Chemical Weapons to Turn Back Invading Argentine Ants”

Although we may think that humans dominate the globe, one Argentine species of ant, Linepithema humile, is making strides to challenge this supremacy. In fact, this invasive species may be part of a colony that is “ the largest of its type ever known for any insect species, and could rival humans in the scale of its world domination” (Walker). This mega colony has spread its reach over several continents, including Africa, Europe, Australia, and North America, and unwittingly humans have played a role in the formation of this colony by transporting these insects in contaminated crates of Argentinean sugar. Unfortunately, the spread of this invasive species has resulted in some serious ecological implications, such as the demise of the native ants inhabiting these conquered territories. The extermination of the native ants has greatly impacted the surrounding ecosystem, because “some native ant species that eat seeds have coevolved with certain native grasses and other plants to become a crucial part of the plant's propagation by carrying the seeds to new areas” ("Native Ants Use…”). Thus, the disappearances of these native species have drastically affected the dispersal and survival of these grasses, and the creatures that feed on or reside in these plants. However, one ant species native to North America, Prenolepis imparis, has decided to take a stand against the onslaught of this foreign invader. The aggressive interactions between these two ant species was documented in the study, Chemical Defense by the Native Winter Ant (Prenolepis imparis) against the Invasive Argentine Ant (Linepithema humile), conducted by Trevor R. Sorrells, Leah Y. Kuritzky, Peter G. Kauhanen, Katherine Fitzgerald, Shelby J. Sturgis, Jimmy Chen, Cheri A. Dijamco, Kimberly N. Basurto, and Deborah M. Gordon. The study first began as Dr. Deborah Gordon and her class were traveling around campus observing anthills as part of her course, The Ecology of Invasion. While observing the different locations, they discovered a fierce battle taking place between the native winter ant and the invading Argentine ant. This was the first documented case where a native ant species has resisted habitat displacement by the Argentine ants. Prenolepis impairs, colloquially known as the winter ant, was able to resist the aggressive attacks of L. humile by employing “a potent defensive secretion” (Gordon DM et al.).
After conducting one-on-one laboratory trials between P. imparis and L. humile, Gordon et al. discovered that the defensive secretion was highly lethal, having a 79% mortality rate. However, the trials also revealed that the winter ants only released this toxic defense “either when vastly outnumbered or in the immediate defense of queen and colony”, which suggests that the manufacture and use of this secretion is very energy costly ("Native Ants Use…”). Nonetheless, the native winter ant has been able to stave off displacement the invasive Argentine species, which will be very beneficial to the subsequent environments that they inhabit. The native grasses that have co-evolved with the native winter ants will be able to propagate successfully, as will the animals that rely on those grasses as food and as a habitat.

Taxonomy:
Argentine Ant Winter Ant
Kingdom: Animalia Kingdom: Animalia
Phylum: Arthropoda Phylum: Arthropoda
Class: Insecta Class: Insecta
Order: Hymenoptera Order: Hymenoptera
Family: Formicidae Family: Formicidae
Genus: Linepithema Genus: Prenolepis
Species: Humile Species: Imparis

Works Cited
Johnson, Craig. "Ants Using Chemical Warfare, Class Project Finds – This Just In - CNN.com Blogs." This Just In - CNN.com Blogs. 08 June 2011. Web. 07 Nov. 2011. <http://news.blogs.cnn.com/2011/06/08/ants-using-chemical-warfare-class-project-finds/>.
"Native Ants Use Chemical Weapons to Turn Back Invading Argentine Ants." Science Daily: News & Articles in Science, Health, Environment & Technology. 07 June 2011. Web. 09 Nov. 2011. <http://www.sciencedaily.com/releases/2011/06/110607131729.htm>.
Gordon DM, Kuritzky LY, Kauhanen PG, Fitzgerald K, Sturgis SJ, et al. 2011 Chemical Defense by the Native Winter Ant (Prenolepis imparis) against the Invasive Argentine Ant (Linepithema humile). PLoS ONE 6(4): <http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0018717>
Walker, Matt. "BBC - Earth News - Ant Mega-colony Takes over World." BBC News - Home. 01 July 2011. Web. 07 Nov. 2011. <http://news.bbc.co.uk/earth/hi/earth_news/newsid_8127000/8127519.stm>.