Coevolution At Risk: Fig-Wasp Relationship Struggles Against Climate Extremes
Climate change and habitat fragmentation threaten the survival of fig wasps, endangering fig trees and the ecosystems they support through specialised pollination.
By Anubha Jain
Published : October 9, 2025 at 12:04 PM IST
Bengaluru: Insects may be small, but their survival holds up entire ecosystems, from the ancient bond between figs and fig wasps to the crops that feed us. As climate change intensifies, rising temperatures and shrinking habitats are pushing these vital pollinators to the brink.
Professor Renee M Borges, Honorary Professor at the Centre for Ecological Sciences (CES), Indian Institute of Science (IISc), and her lab have worked extensively on decoding the fig-fig wasp relationship. In an exclusive conversation with ETV Bharat, Borges shared how heat, habitat loss, and shifting seasons are silently rewriting the lives of insects and what that means for the world.
Pollinators: The invisible pillars of life
"Pollinators play a vital role in the production of nearly 70 per cent of the world’s crops. In India, staple grains such as rice and wheat, along with corn in many regions globally, are primarily pollinated by wind, a process that does not involve any living organisms. In these crops, the male and female reproductive parts must unite naturally for seeds or grains to form," Borges explained.
"In contrast, legumes, pulses, and most fruits depend on pollination by insects or other organisms. Without these pollinators, the process cannot occur, leading to reduced yields of crops that are essential sources of micronutrients, proteins, and vitamins in our diets," she added.
Fig trees: Keystone species sustaining tropical ecosystems
Fig trees hold great ecological importance in India and are considered keystone species. In an arch, the keystone is the central stone that supports the entire structure. If it is removed, the arch collapses. Similarly, fig trees play a crucial role in maintaining the balance of their ecosystems, Borges said.
A fig is a hollow, fleshy structure called a syconium, lined with hundreds of tiny flowers inside. In the unique fig–wasp pollination system, tiny wasps grow inside closed figs that provide both food and shelter. Once mature, male wasps emerge first, mate with females inside the fig, and dig exit tunnels before dying. The fertilised females then collect pollen, escape through these tunnels, and have just 24–48 hours to find another receptive fig to pollinate and lay eggs. The flowers they use for egg-laying develop into galls that nourish the larvae, completing the remarkable cycle of life and pollination. Throughout the year, fig flowers are the only places where fig wasps can live and reproduce.
Borges noted that fig trees produce fruits year-round, ensuring a continuous exchange of pollen and pollinators. These fruits also serve as an essential food source for a wide range of animals—monkeys, primates, birds, and even humans. During times when other food sources are scarce, figs become a lifeline for many species. Since they sustain such a vast network of life and provide resources throughout the year, ecologists refer to fig trees as keystone species.
"This remarkable interdependence between figs, their pollinators, and other animals is what inspired me to study this fascinating keystone group."
The fig–wasp relationship: A classic example of coevolution
She explained that the fig–wasp relationship is a classic example of coevolutionary mutualism. Co-evolution occurs when two species evolve together, developing traits that are interdependent and complementary. There are about 800 species of figs worldwide, and each fig species has its own unique pollinator wasp.
"In the case of Ficus racemosa, which I focused on, the pollinator species is highly specific—it cannot pollinate any other fig species. This tight evolutionary linkage means that if the pollinator population declines due to climate change, the process of fig pollination—and consequently fig reproduction—will be disrupted," Borges said.
Rising heat and erratic rainfall put fig–wasp survival on the line
When asked what other climate-related factors, apart from temperature, threaten the fig–fig-wasp relationship, Professor Borges said that according to various studies conducted under laboratory conditions—since such experiments can only be carried out in controlled environments—fig wasps cannot survive temperatures above 37–38°C. However, in cities like Bengaluru, temperatures are now exceeding 40°C, and in several parts of the country, they even cross 45°C. Ecologists and environmentalists are deeply concerned about this trend.
"Fig wasps rely on the wind for dispersal. They rise above the forest canopy, where winds are stronger, to reach other fig trees. However, we lack accurate temperature measurements at the different heights where these wasps travel," she said. "Considering that a fig wasp lives for only 24 to 48 hours, it must find and enter another fig within this short time span. If temperatures at these flight heights are too high, the wasps’ survival and successful pollination could be at risk.
Adding further, she said that in addition to temperature, rainfall patterns also influence fig wasp activity. Observations show that heavy rain, cloudy weather, and irregular monsoon patterns can delay or reduce the arrival of fig wasps at fig trees, further impacting pollination.
A perfect rhythm: How fig trees and wasps stay in sync all year
Talking about how fig trees ensure a continuous supply of receptive figs throughout the year, Professor Borges explained that fig trees bear flowers enclosed within their inflorescences, which develop over a period of about two months, depending on the species. The wasps’ gestation period inside these fig “nurseries” also lasts around two months, and all the figs on a single tree remain synchronised in their development.
"Once the wasps emerge from a particular tree, they cannot find suitable figs on the same tree to lay their eggs and begin the next generation. Instead, they must travel to another tree that is at a different stage of its cycle," she said.
In nature, different fig trees reach these stages at different times. This offset in developmental cycles allows one tree to release pollinators while another receives them. As a result, pollen is not recycled within the same tree but is transported by the wasps to distant trees, ensuring effective cross-pollination and the continuation of both species, she added.
Limited energy reserves make fig wasps vulnerable to habitat gaps
Borges stressed that habitat fragmentation or urbanisation worsens the risks for these tiny wasps. She explained that fig wasps emerge with only a limited amount of energy, which has been measured and quantified in laboratory studies. Since they rely entirely on the energy stored during their development inside the fig nurseries, they have no means to replenish it once they emerge.
Therefore, habitat fragmentation poses a serious threat; if the distance between fig trees becomes too great, the wasps may not have enough stored energy to reach their next destination. This is the key problem caused by habitat fragmentation, she said.
Climate threats hit fig wasps and bees differently
Emphasising the cascading effects that might arise in tropical ecosystems if fig pollination fails, and comparing them with threats faced by other pollinators such as bees, she explained that if a fig pollinator is lost, no other pollinator can replace it within the fig system, as this relationship is a classic example of coevolution and specialisation.
In contrast, bees are more generalised in their choice of food sources—whether domesticated or wild, they can switch to another plant if one resource becomes unavailable. However, climate change poses a serious threat not only to fig wasps but also to honey bees, as both struggle to survive or fly when temperatures rise too high—typically above 40°C, she noted.
Pollinator-friendly habitats and supporting microclimates can safeguard the fig-wasp mutualism
In response to a question about the interventions or policies needed to safeguard the fig–wasp mutualism, she emphasised that the primary focus should be on preventing habitat fragmentation. It is essential to ensure that fig trees remain within the flying range of the wasps. Fig wasps cannot feed outside the figs and live for only 24 to 48 hours. If they are unable to reach another fig tree within that limited time, their life cycle cannot continue, and since they cannot feed as they lack a feeding apparatus, providing feeding stations is not an option.
“This mutualism is fundamentally threatened by the lack of connectivity between fig trees,” she said, “and that connectivity depends entirely on the flight capacity of the fig wasps.”
Responding to how her findings could inform broader insect conservation strategies under climate change, Professor Borges said that it is crucial to develop a deeper understanding of microclimates—the local climate conditions around bee hives and fig trees. She explained that increasing vegetation can help cool the environment and reduce extreme temperature spikes. Similarly, providing water bodies can help bees and fig wasps ventilate and cool themselves, but unfortunately, such water sources are often missing in the areas where these pollinators live.
“If we can create more pollinator-friendly habitats with flowering plants and maintain a favourable microclimate within urban landscapes, we can support and sustain these pollinators,” she said. “This is how we, as citizens, can contribute to giving life back to them.”
