This Ficus virens strangler growing next to the Observation Tower at the Maliau Basin, is an excellent example of how a strangling fig slowly kills the host tree.
Ficus roots have a peculiar ability for anastomosis where adjacent roots grow together into a combined network. The network then encircles the host tree. The anastomosing roots undoubtedly put some pressure on the fluid transport vessels in the cambium under the bark of the host which deliver water and minerals from the roots to the leaves (xylem) , and sugars from the leaves to the roots (phloem). The phloem channels are softer and closer to the bark than the xylem, so the starving host probably finds it difficult to outgrow or compete with the fig. At the same time the roots of the fig compete with the roots of the host for water and minerals and the leaves of the fig steal sunlight from the leaves of the host. This very effective 3 pronged attack on the host means that once a strangler has managed to encircle the host tree, the host is usually doomed.
There is no benefit to the fig tree if the death of the host tree happens too quickly, because then both the tree and the host will fall to the ground, so the “strangling” process has evolved to take place very slowly over a few years until the roots of the fig tree are strong enough to support the fig tree by themselves.
The Ficus virens fig illustrated in the article above is growing near the Observation Tower at the Maliau Basin in Sabah. The tree in the photo above growing behind the Observation Tower is Octomeles sumatrana (Local name Binuang) which is a fast growing tree normally found along river banks in Borneo.