GrrlScientist writes:

In a remarkable, but accidental, real-life experiment demonstrating the ecological connections between all life regardless of how great or small, a study recently came out that documents how a tiny ant is affecting the mighty lion on the savannahs of Kenya.

This ant is invasive and it’s far from home. It probably arrived from the island of Mauritius, located in the Indian Ocean, early during the last century, and began establishing itself in the Ol Pejeta Conservancy in Kenya around 20 years ago.

“It showed up in people’s houses and other centers of human activity,” said the study’s senior author, animal ecologist Jacob Goheen, a Professor of Zoology & Physiology and of Botany at the University of Wyoming. Professor Goheen’s expertise is linking theory with data as he works to better understand community dynamics and structure, animal-plant interactions, and conservation biology.

“To the best of our knowledge, it was introduced in bushels of produce from somewhere in the Indian Ocean,” Professor Goheen stated.

The ants, known as big-headed ants, Pheidole megacephala, build and live in huge underground metropolises, like most of the ant species that you’re familiar with. After they invaded, these small ants hunted down and killed the native acacia ants, and ate their pupae, and eggs.

The native acacia ants live symbiotically with whistling thorn acacia trees, Vachellia drepanolobium. In exchange for food and shelter provided by the trees’ bulbous thorns, acacia ants act as bodyguards, vigorously protecting their landlord-trees from predation by hungry giraffe, elephants and other large herbivores.

“Much to our surprise, we found that these little ants serve as incredibly strong defenders and were essentially stabilizing the tree cover in these landscapes, making it possible for the acacia trees to persist in a place with so many big plant-eating mammals,” said the study’s second co-author, ecologist and conservation biologist Todd Palmer, a biology professor at the University of Florida.

Acacia ants’ bites are quite painful because they contain formic acid, which is the caustic burning chemical that makes many insect stings (and stinging nettle attacks) very painful. The native acacia ants are especially well-equipped for attacking hungry elephants by swarming up their noses, biting madly all along the way. This mutually beneficial ecological relationship between acacia trees and acacia ants is known by biologists as a mutualism.

Unfortunately, invasive big-headed ants offer no such protection to acacia trees, and because they kill the physically larger acacia ants, the trees are suddenly rendered vulnerable to elephant attacks. As a result, elephants began crushing and eating the acacia trees, destroying the tree cover. Thus, after invasion by big-headed ants, the landscape was transformed into a much more open habitat, largely devoid of brush, small trees and woodland. [Continue reading…]