Don’t care a fig? You’d better

An extraordinary relationship between two living entities that goes back about 75 million years, since the time of the reign of the dinosaurs, is bound to be that much more special and specialised. The ubiquitous and life-giving fig trees, all 800-plus Ficus species, depend on a single family of tiny pollinators called the fig wasps to pollinate them. In turn, the life cycle of the fig wasp dramatically begins and ends with a fig. These obligate mutualists have weaved an evolutionary saga so fascinating and exerted a biological force so powerful, that they have shaped the tropical forest ecosystems into the rich treasure troves of biodiversity that we know them to be. Without the fig wasps, fig trees would cease to exist. And without the fig trees, fig wasps wouldn’t be able to procreate, eventually going extinct.

Once inside, she quickly finds female flowers to lay her eggs in using her specialised egg-laying organ called the ovipositor. Along with the eggs, she simultaneously also deposits the pollen she has inevitably carried from the fig in which she was born and emerged from, only about 24 hours ago. Thus, the female flowers are fertilised, eggs are laid and secure, and the female fig wasp having lived out her short life (read very short life) of 1-2 days dies inside the very fig she has successfully pollinated.

Soon the eggs hatch inside the mature fig, usually with male wasps emerging first, blind and wingless, only to impregnate their ‘sister’ brood of still-to-be hatched females. The females hatch, already pregnant, and exit the fig through a hole the males have bored for them. The male wasps, thereby, fulfil their life’s only purpose: impregnating the females and digging them an escape tunnel, after which the males die, never having left the premises of the fig! The gravid (pregnant) females emerge, covered in pollen inadvertently picked up from the male flowers in the syconium, and urgently set out in the search of host fig trees to nest in and lay their eggs. And thus, the cycle plays out over and over again. A female fig wasp is bound by very little time and burdened with an enormous task.

Sadly, human-induced global warming seems to be running a fatal interference in this delicate, mutually obligate, ancient relationship between the fig trees and fig wasps. In the past few years, biologists have uncovered a disturbing trend in which the fig wasps are proving to be especially vulnerable to rising temperatures. Several species of fig wasps are showing lesser and lesser thermal tolerance to the escalating temperatures across their tropical range. Result? Shortened lifespans! For these already very short-lived insects, every hour counts. So, their life duration getting cut short, even by a few hours, could prove to be devastating not only for the fig wasps, but also their hosts, the fig trees.

Here is the thing about fig trees. They are considered to be ecologically, and even culturally, the most important group of plants in the world. The likes of the Indian banyan tree (Ficus benghalensis), sacred fig tree (Ficus religiosa), cluster fig tree (Ficus racemosa), Sycamore fig tree (Ficus sycomorus) among others, sustain thousands of species of birds, mammals, reptiles, and insects. Many forest ecosystems revolve around fig trees as a critical food source. But if global warming were to rock the boat of fig tree-fig wasp mutualism too much, the forest systems that it sustains will proceed to unravel.

Scientist Mike Shanahan once said, rather eloquently, “In the plant kingdom, fig trees really are first among equals.... Fig trees feed more species of wild animals than any other group of plants, but only if their wasp partners are there to pollinate their flowers…The fates of fig trees, fig wasps, and fig-eating birds and animals are all bound together.”

Only time will tell if this obligate mutualism between the mighty fig trees and the diminutive fig wasps will stand the test of time dominated by humans.