The Queen of Trees Photo Essay: An Extraordinary Ecosystem
The Queen of Trees
The sycomore fig tree, the African queen of trees, begins life as a tiny seedling, then gracefully ages to over 100 years old. This regal tree is the centerpiece of an extraordinary ecosystem, producing several tons of fruit a year and feeding a greater variety of animals than any other kind of tree in Africa. The animals that feast on the tree's fruit, in return, disperse the fig seeds far and wide. But other creatures who harvest the queen's sweet and nourishing sap may damage the tree in the process.
The fig wasp is crucial to the queen's survival; without it, the sycomore would not be able to pollinate and reproduce. The process begins when female wasps are attracted to the scent of the microscopic flowers blooming within the fruit of the African queen. Loaded down with fig tree pollen and fig wasp eggs, these tiny wasps enter the fig via a sliver of an opening. Once inside, they pollinate the flowers and lay their eggs before dying. Some of the flowers will become seeds and others will become nurseries for fig wasps. The tree protects each wasp egg by creating a capsule (or gall) around it. The gall nourishes and protects the egg as it matures. Upon hatching, the male wasp uses its powerful jaws to cut through the female wasp's gall in order to mate with her. Eventually the male wasps create a tunnel so that female wasps, covered in fig pollen, can leave the tree and fly off to start the remarkable story all over again.
Parasitic wasps attack the fig wasp nursery inside the tree's fruit. They drill into the fig using a long ovipositor -- an egg-laying device that works like a hypodermic needle. Forced deep inside, the ovipositor will deposit one of the parasitic wasp's eggs on a developing fig wasp. The grub that hatches will kill the fig wasp and take over its gall. However, if the parasites are too successful and no male fig wasps survive, they too are doomed, for they rely on their help to escape from the fig. Without them, they will be trapped inside, and die.
Ants play many roles in this ecosystem, including serving as the sycomore's ally against parasitic wasps. Ants attack the parasitic wasps as they attempt to penetrate the fig. Ants also care for the little nymphs produced by a bug called Hilda, guarding them from predators and helping them feed. But the ant's help is not purely altruistic, for each nymph has a hollow piercing mouthpart it uses to tap into the fig sap. The sweet liquid passes quickly though the nymphs and emerges as a sweet treat for the ants that they could not access on their own.
Hornbills build their nest inside a hollow in the fig tree. The female lays her eggs, then seals herself inside the hollow trunk, leaving only a slit through which the male can feed her. The hornbill must plan its nest-building very carefully -- the female has to lay her eggs so the chicks hatch just after the rains, when food will be plentiful. In lean times, the chick with the best chance of survival gets to eat first and takes most of the food.
Nematode worms, also called roundworms, can be found in almost all ecological niches. In this ecosystem, they enter the queen of trees by stowing away in the body of the tree’s pollinator and ally, the female fig wasp. They burrow into her body and slowly eat her alive as she makes her way to a new tree and a new fig. Once there, these microscopic parasites burst out and kill her -- beginning a new life cycle among the eggs she leaves behind.
Monkeys are opportunist feeders, and the queen of trees creates many chances for easy snacking. They are drawn to the cicadas that feed on the sticky-sweet sap inside the trees. Monkeys love not just the cicadas, but the shower of sap they vent while feeding on the tree. Ripe figs are also a great treat but they are careful to discard those full of parasites.
More than 100 varieties of birds eat the fruit produced by fig trees, helping them spread their seeds in the process. New trees can sprout wherever the birds perch after feeding. The green pigeon in particular loves figs. It will fly miles from its nest in order to feed on the sycomore. After eating as many figs as it can hold, the pigeon makes the long trek home, where it feeds its chicks on a milk of liquid figs.
One would think that with all the figs falling from the tree onto the ground, new fig trees would sprout everywhere, but this is not the case. Seed bugs, which live and breed at the foot of the African queen, eat all of the seeds that fall. These specialized insects eat only fig seeds, and though they do not overtly damage the tree, they do keep its seeds from spreading.
Fruit bats are the most important dispersers of the fig tree's seeds. Importantly for seed dispersal, the bat rarely eats in the tree, but instead carries the fruit a short distance away. It doesn't eat the entire fig, but sucks out the juice and discards the seeds. Beneath its perch, a tiny fig tree garden will sprout. Each bat eats half its weight in fig pulp every night.
Even elephants, which spend as much as 16 hours a day eating, enjoy the sweet goodness of figs. African elephants also snack on fig tree leaves and twigs. These giants travel far and wide and are thus able to disperse the fig tree's seeds during their journeys.