Image by Couleur from Pixabay
We might not all recognize them, and we might not recognize all of them but fig trees are among the native flora that have come to settle in cities with us.
Some are intentionally planted in urban areas, while others continue to appear spontaneously, self-sowing, even in the less than ideal habitat that is the city landscape.
Fig plants belong to the genus Ficus and there are over 700 species of fig species spread throughout the tropical and subtropical regions of the world. Throughout Peninsular Malaysia alone, there are around a hundred Ficus species native to the peninsula.
This large group of flowering plants has a diverse growth pattern and, depending on species, can be
- large trees,
- climbers or
- epiphytes (plants which live on the surface of other plants for support)
In the wild, these plants are important sources of food and shelter for wildlife. In some natural ecosystems, they are so important that they are described as keystone species.
Keystone species are organisms in a community that have a great influence on other members, regardless of their actual size or number. Although all organisms will have a role to play in a given habitat, the presence of keystone species can be critical to the welfare of the other organisms.
But what role can these plants play in cities?
The Ficus species that survive in cities tend to be those that come from relatively dry and exposed natural habitats like the edges of forests. Or they are the kinds that are capable of sprouting (from seeds dropped by animals) from crevices, to cling to and grow on vertical surfaces like stone walls.
While not all species of native figs can tolerate city conditions, those that do, share the features that make these groups of plants valuable in the wild. They produce fruits that a large variety of urban wildlife, including squirrels, shrews, primates, bats, and fruit-eating birds, find palatable.
The dense crowns and surface roots of fig trees on the other hand, are of value to urban residents where they can offer shade and stabilize and enrich soil cover. Fallen leaf litter decompose and return nutrients to soil and the spreading, surface roots of the trees help prevent soil erosion by improving the soil structure.
Fig trees will also do what trees do so well—provide spaces (holes, branches) for animals to build shelter and nests. In return, animals spread the seeds from fig fruits far and wide.
But there is one animal, an insect, with which figs have a somewhat unique relationship. One which determines how it flowers and fruits, thereby helping make it the important food source that it is.
The very old tale of the fig and the wasp
For each fig species, there is a single wasp species capable of transferring the flowers’ pollen to allow the plant to reproduce. The wasp species in turn relies solely on that fig flower to complete its life cycle (to live in and lay its eggs). One would not survive without the other.
As important as these two groups of plants and insects are to each other, their interdependent relationship affects other life forms as well.
The reason that fig plants are considered keystone species is tied to this relationship with wasps. In order for there to be enough chances for the short-lived wasps to find flowers or fruits to live in, individual plants produce flowers and fruits at different times throughout a year.
This means that there is almost always a fruiting fig tree. Even when other plants in some forest communities fail to produce fruit or are not in season, fruit eating mammals and birds would be able to find a supply of food at a fig plant.
Nature in cities
The fig tree is a good example of a tree that is traditionally popular, capable of withstanding urban conditions and has ecological significance (for both humans and wildlife).
There are many factors that dictate what trees can be planted without disrupting roads and spaces for pedestrians, residents and drivers. Nevertheless, the urban habitat consists of such a variety of land types and structures that, by understanding the ecology of wildlife, cities may very well be able to meet both practical and ecological concerns.
Lok, A. F. S. L., W.F. Ang, B.Y.Q. Ng, T.M. Leong, C.K. Yeo & H.T.W. Tan (2013). Native fig species as a keystone resource for the Singapore urban environment. Singapore: Raffles Museum of Biodiversity Research.
Shanahan, M., So, S., Compton, S. G., & Corlett, R. (2001). Fig-eating by vertebrate frugivores: a global review. Biological Reviews, 76(4), 529-572.