A friend’s enemy may be a friend - January 11, 2008
In the complex world of biology, getting rid of one of your predators might do you no good at all.
Acacias on the savannah supply ants with thorns to nest in and nectar to drink. In return, the ants swarm against herbivores that eat the acacias. But when Todd Palmer, a zoologist at the University of Florida, and colleagues fenced off the trees from large herbivores they found that both trees and ants did badly (research paper in Science).
Ten years of herbivore-exclusion meant less nectar and housing was provided to the ants – why provide room and board to a lodger you don’t need? Unfortunately for the acacias that meant another ant species got a foothold on the trees, and trees occupied by this new species “suffered increased attack by stem-boring beetles, grew more slowly, and experienced doubled mortality relative to trees occupied by the mutualistic ant”, Palmer et al report.
“Throughout sub-Saharan Africa these large mammals are threatened by human population growth, habitat fragmentation, over-hunting, and other degradation, so we have to wonder how their loss will affect these ecosystems. The last thing you would think is that individual trees would start to suffer as well, and yet that’s exactly what we see,” says Palmer (press release).
African animals are always a good bet for news reporters and this story is no exception: coverage in Scientific American, NY Times, Telegraph, BBC, SF Chronicle, AFP.
Image top: African savannah scene / Robert Pringle
Images lower: Giraffes around the ant-plant / Todd Palmer ; Elephants around the ant-plant / Nathan Gregory ; Ants around the ant-plant / Todd Palmer