Fan Palms have an important partnership with figs that germinate in the brown fabric at the neck of the tree and start their lives about 25 metres above ground at the top of the tree trunk. The fig roots grow downwards, as fine threads seeking sustenance, until they reach the soil and nourishment. Then they start to thicken and strengthen forming woody trunk-like roots that slowly surround the trunk of the host tree. This process takes many years as the seedling fig, growing up to the light, emerges above the canopy and continues to fruit and contribute to an expanding network of roots that fuse together to surround the host tree.
Fig, Ficus species, seeds can fall anywhere, direct from the tree from emergents that soar above the canopy seeking light, while roots grow downwards, seeking nourishment. Some fig roots have been measured at more than 100metres, as they spread outwards, anchoring the fig to the ground. Birds and flying foxes can drop fig seeds in their excrement as they alight on branches. Figs are in high demand within the rainforest for a multitude of consumers and are in supply throughout the year. Figs are not the only seeds that can grow as stranglers. Umbrella trees, Schefflera actinophylla, also seeded by birds start to grow on host trees and are strong and thick enough to strangle. Figs are more successful and more all-embracing in their growth, using the tree as a support while their roots and branches develop and strengthen. They do not squeeze the tree. It is the outward growth of the host tree that causes strangulation. If the tree is mature, it does not expand around the girth to any great extent, and the most likely outcome for the host tree is death from old age. If the strangler is big enough and strong enough it will continue to support the host tree, which crumbles and decays, providing nourishment for the strangler. The fig will remain standing as a hollow tree to maintain the canopy for the benefit of the ecosystem.
Fan Palms are tall slender trees with straight narrow trunks. They do not grow huge girths and therefore they are less likely to die of strangulation. Strangler figs occur more commonly on fan palms because of their habit of growth and the readily available food supply at the neck of the plant. It’s easy to see the prevalence of strangler figs on fan palms compared with other trees and the bonding effect that ties the forest together from top to bottom. Strangler figs on fan palms look like huge pythons. United we stand, thanks to the figs and the fan palms. This is particularly important during cyclones, when gale force winds could flatten a rainforest.
Ficus species rely on fig wasps to pollinate the flowers. Each species of ficus, and there are approximately 850 species in the world, has its own species of fig wasp. A female fig wasp enters the fruit through a small channel at the top of the fruit and squeezes its way into the receptacle to lay its eggs. The female often loses its wings as it enters, but its last remaining function is to lay the eggs. It then dies. The eggs hatch out into larvae, which feed on parts of the fig, and the female wasp, until they reach maturity and hatch out into fig wasps. Male larvae hatch out first and the male fig wasps are born without wings and without eyes. There have two functions in life. The first one is to mate with the female fig wasps as they hatch out, having both eyes and wings, and the second is to eat out the opening channel to enlarge it so that the female can emerge without loss of wings and can fly to another fig, of the same species. The male then dies. He has completed his work. The females survives up to 48 hours before it, too dies. It has to find another fig, and has been known to travel up to 160kms in 2 days, to find the right species. There are 15 different species of fig on our 160acre block of rainforest, therefore 15 different species of fig wasp and many other fig wasps that feed on, but are not part of, a symbiotic relationship with the fig.
