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Ant In Tree Depends On Giraffe January 12, 2008

Posted by tkcollier in Enviroment.
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BBC NEWS | Science/Nature | Big mammals key to tree-ant team
At first it may seem counter-intuitive: that preventing large African herbivores from browsing Acacia trees decreases their growth.

Acacia trees provide ants with swollen thorns, which serve as nesting sites; and nectar, which the ants collect from the bases of Acacia leaves. In return for this investment, ants protect the tree from browsing mammals by aggressively swarming against anything that disturbs the tree.

The researchers disrupted this relationship by fencing off six plots of savanna land in Kenya by an 8,000-volt electric fence for 10 years. Herbivores, such as giraffes and elephants, were no longer able to feed on the trees, causing a change in plant-ant dynamic.

Due to lack of housing and food, the mutualistic ant species becomes less aggressive, its colony size decreases and it loses its competitive edge.

“The net result is a community-wide replacement of the ‘good’ mutualist ant by a decidedly ‘bad’ ant species that does not protect the trees from herbivores, and actually helps a wood-boring beetle to create tunnels throughout the main stem and branches of the acacia trees, which the bad ant then uses as nesting space,” Dr Palmer explains.

Trees occupied by this antagonist ant grow more slowly and experience double the death rate compared with trees occupied by the mutalistic ant. Thanks to EPIC for passing on this example of the Laws of Unintended Consequences

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