By Soham Kacker
A tall glass of kokum sharbat on a hot summer day is pure magic! This small, red, sweet-sour fruit is a favourite in South India, a vital ingredient in traditional medicine, and a delicious part of Konkan cuisine.
The kokum tree Garcinia indica belongs to the genus Garcinia – a group comprising over 400 species that are widely distributed across Africa, Asia and Oceania. Other well-known members of the genus include the kodumpulli, Garcinia gummi-gutta, the mangosteen Garcinia mangostana, and the bitter kola nut Garcinia kola. India is home to 35 species of Garcinia, of which 17 are endemic hardwoods found in the coastal Western and Eastern Ghats forests of India.
Garcinia fruits tend to be delicious (no surprises there!), but this poses a unique evolutionary challenge for them. Often sweet and fleshy, the fruits of several species are relished by forest animals, but the seeds in particular – packed with fats and oils – are a key source of nutrients for mammals such as the Nilgiri langur and the Malabar giant squirrel. Snacked on by these animals, Garcinia seeds are often damaged – so how do they survive? One way would be to evolve toxins to prevent seed predation. But this would mean relinquishing important services the langurs and squirrels provide: seed dispersal. Garcinia has evolved a truly ingenious strategy to balance the odds.
In most conventional plants, a seed is a specially-crafted care package for a particular group of cells called the embryonic axis. This contains a tiny cluster of cells, which rapidly divide to form the root and shoot when the seed germinates. For instance, it is the small structure on the inside of a peanut, which seems to hold the two halves together. The rest of the seed acts as a food reserve and protective covering to ensure the embryonic axis has everything it needs to grow into a seedling.
However, Garcinia species have chosen to do away with this blueprint! A species from the Indo-China region – Garcinia xanthochymus – has evolved to spread those embryonic cells all over the seed mass, rather than clustering them at one end. When a seed is damaged, say bitten in half by a foraging squirrel, embryonic cells in both halves can begin to rapidly divide, and clone themselves into roots and shoots – the seed remains almost unaffected! Experiments on Garcinia imberti have shown that seeds can sustain a loss of up to 75 per cent of their mass, and still produce a healthy seedling! In any other plant, this would be practically impossible. Garcinia evolved this unique seed structure as an evolutionary response to the high predation pressure it faces in its native forests.
There are some threats with which Garcinia species cannot cope. Many species of the genus struggle to germinate and form viable populations on account of dwindling and increasingly disturbed habitats. The species Garcinia imberti is considered critically endangered, and the species G. cadelliana, endemic to South Andaman Island, is thought to be almost completely extinct. In 2012, an American celebrity doctor claimed that Garcinia extracts were a powerful weight-loss supplement. The trend saw Google searches for ‘Garcinia’ skyrocket, and a multinational market was created almost overnight, which branded the plant as a wonder-drug. The claims had weak scientific basis, but that didn’t stop sales. Fruits were collected from the wild to supplement the yields from farms, which had earlier catered exclusively to a hyperlocal market. Instances such as these make one wonder how gradually evolved species have managed to survive impossible odds, but may succumb one day to a pseudo-scientific Internet trend. Garcinia has survived the giant squirrel, let’s hope it can also survive the health industry.
Further reading:
Anto, M., et al. ‘Fruit Predation and Adaptive Strategies of Garcinia imberti, an Endangered Species of Southern Western Ghats.’ Current Science, Vol. 115, No. 12, 2018, p. 2315, https://doi.org/10.18520/cs/v115/i12/2315-2321.
Wang, Zhenyu, et al. ‘Cloning Capacity Helps Seeds of Garcinia xanthochymus Counter Animal Predation.’ Ecology and Evolution, Vol. 11, No. 18, 2021, pp. 12639–12650, https://doi.org/10.1002/ece3.8008.
Soham Kacker is passionate about plants and has apprenticed at the Auroville Botanical Gardens and the Aravalli Biodiversity Park. Based in New Delhi, he is currently a research student at Ashoka University, focusing on plant ecology and conservation.
