Crisp lines of light begin to play out across the landscape. As the morning light grows, blades of grass take shape and, amongst rocky outcrops, green acacia breaks the yellow and gold of the savannah ...

Acacia trees are a prominent feature of the East African savannah. They're also a classic example of the long-standing and complex relationships between plants and insects, in this case acacia ants.

In the 1960s, Penn biologist Dan Janzen, as part of earning his Ph.D., re-described what has become a classic example of biological mutualism: the obligate relationship between acacia-ants and ...

If animals and plants can’t defend themselves, they often form partnerships with bodyguards. Wasps use zombified caterpillars. Corals recruit goby fish. And acacia trees hire ants. The ants defend the ...