EPOW - Ecology Picture of the Week

A Common, 
Edible Strangler

Strangler Fig (Ficus watkinsiana), Family Moraceae
Queensland, Australia

Explanation:  This network of stems is slowly choking the life out of its host tree, like some arboreal python squeezing its prey to death in slow motion.  This is the typical life history of a strangler fig tree.  

Strangler figs belong to the genus Ficus which boasts about 800 species throughout the world, mostly in the tropics and southern hemisphere.  The species presented in these photos is found in far eastern Australia and is one of about 40 Ficus species found in that country alone.  

Strangler figs are wonderful examples of the complexity of nature's interactions, and I'm not just referring to its reticulate growth form.  These figs begin as seeds high on the branches of other trees, and grow aerial roots downward, wrapping around the trunk until they hit the ground.  There, the roots dig into the soil, sucking nutrients that would otherwise feed their host tree.  Bit by bit, the host tree dies, often leaving a hollow network of fig stems in its place, like some weird ghostly shell.  

The shell trunk of the remaining fig then becomes important habitat for a variety of invertebrates, bats, reptiles, birds, and others.  Wildlife often then eat the fig's fruits -- which are sought by many species -- which pass through their digestive system, and the seeds are then transferred to another host tree where the seeds germinate and the cycle begins again.  The fruits themselves are pollinated by the gall wasp, the female of which digs into the fruit to lay eggs and thusly transfers pollen to the plant.  

Thus, strangler figs are at the center of a remarkable array of relationships including gall wasps that serves as pollinators, wildlife species that serve as seed dispersers, and host trees that support their growth.  

One study (Male and Roberts 2005) determined that this fig species generally selects host trees based on size; the bigger the host, the more likely it will be used by the fig.  After size, host trees with rougher bark might be then selected, as that would provide the fig with better ways for its aerial roots to grasp the trunk.  

Seeds of Ficus watinsiana are sold for cultivation.  

 

Information: 
     Male, T.D. and G. E. Roberts.  2005.  Host associations of the strangler fig Ficus watkinsiana in a subtropical Queensland rain forest.  Austral Ecology 30(2):229-236.