The Sacred Bodhi Tree

During my visits to the Buddhist temples in Chiang Mai, I realized that there is a sacred tree at the entrance of these temples. This tree is usually surrounded by a short wall with Buddha statues around it – this is Ficus religiosa, the sacred fig. This is a very important tree in Buddhist culture since it was under a Ficus religiosa where Buddha attained enlightenment while meditating.

The original plant was in India, and cuttings were taken from it and transplanted to other places across the Buddhist world at the time to keep the sacred tree safe. One of the cuttings was taken to Sri Lanka, and it is the only surviving member of the original plant. With more than 2500 years old (!!!) this is the oldest living angiosperm on record! The most impressive thing is that the Ficus religiosa found at the entrance of the temples all around the world (including Thailand), are all clones of the original tree in Sri Lanka (in Mahabodhi Temple) that grew from cuttings of the mother plant and are thus all genetically identical!

Now, back to botany… Ficus belongs to the Moraceae family – the figs. As some of you might already know, this family is very widely dispersed in the tropics and the presence of white sap is one of the field characters recurrently used to identify the family. But the flowers and the fruits are the most characteristic and weird features, with a very specific pollination syndrome. To begin with, figs are not fruits – they are false fruits, multiple fruits (tricky!). So the fig is actually a group of very small aggregated fruits, enclosed in a structure that we call syconium (the fig). The syconium is also the inflorescence, and encloses all the male and female flowers. The apex of the syconium has a hole (ostiole) from where the specialized pollinator comes into the inflorescence; the pollinators of Ficus are usually very small wasps. As I mentioned, these plants are known for having very strange flowers, and in China they are also known as the fruits without flowers, since you can never see the flowers as they are enclosed in the syconium. The truth is also that figs have usually 3 types of flower in the same inflorescence – male flowers are found surrounding the ostiole and two types of female flowers are found in the inner part of the syconium, type one has long styles and type two has short styles. The pollination is carried out by wasps that visit the syconium to lay their eggs and they lay their eggs in the short styled female flowers.

The most interesting thing about this pollination syndrome is the very close co-evolutionary relationship between species of figs and wasps. Most of the time one wasp is specialized on the pollination of one single species of fig. A good example for this is that in Hawaii, where around 60 species were introduced, but only 4 wasps were introduced, so only four species of figs are pollinated to produce viable seeds.