Acacia Trees Get Ants Hooked On Sap, Turning Them Into Their Bodyguards
Central American acacia trees are basically thugs, it turns out: they get ants hooked on their sugary sap and then become the ants' only digestible food source, forcing the ants to defend them from leaf-eating enemies. After the ants take their first sip of sap, they can't stop, according to new research published in Ecology Letters.
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"It was surprising to me that the immobile, 'passive' plant can manipulate the seemingly much more active partner, the ant," said study author Martin Heil of Cinvestav Unidad Irapuato in Mexico.
The acacia tree turns the ants into little drug addicts by injecting its sap with chitinase enzymes. (Pay attention, because this is a little confusing.) These chitinase enzymes ruin ants' invertase enzymes, which are necessary to breaking down the sucrose ants like to eat. The ants now have to get their invertase from somewhere, so they end up getting it from the very thing that destroyed their invertase abilities to begin with: the acacia tree. The tree's sap contains both sucrose and invertase, and this invertase-sucrose combo meal becomes the only way the ants can eat. Other food sources could provide sucrose to them, but not sucrose and invertase together. So the ants get locked into a proprietary eating system.
"Ain't nature grand?" ecologist Todd Palmer of the University of Florida told National Geographic (Palmer wasn't involved in the study). "What looks from the outside as another case of digestive specialization appears to be a sneaky manipulation on the part of the acacia to increase ant dependence."
And the ants will defend the acacia tree to the death, even though it's an abusive relationship. Remember that the next time you're looking at a lush forest and someone tells you how peaceful it seems.
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