Earth's quiet engineers: What happens when common ant species disappear?

Ants are everywhere – underfoot, under leaves, and under-appreciated. While often overlooked, these tiny insects carry immense ecological weight. Their roles go far beyond scavenging crumbs at a picnic. Each ant species contributes uniquely to keeping ecosystems alive.

Ants aerate soil, disperse seeds, control pests, and interact with plants in complex mutualisms. They are vital to the everyday operations of ecosystems around the world.

A recent study published in Nature Ecology & Evolution puts ants at the center of an ecological experiment with far-reaching implications.

Led by scientists from the University of Western Australia, CSIRO, and James Cook University (JCU), the study investigated what happens when dominant ant species are removed from their environment.

The findings offer insight into the resilience of natural systems – but also a warning. While nature compensates, it may be doing so at a cost few can see coming.

Nature has backup ant species

When the researchers removed three common ant species – Iridomyrmex purpureus, Pheidole ampla perthensis, and Tetramorium impressum – they expected a drop in ecosystem performance. These ants were key players in their local environment, handling everything from seed dispersal to scavenging.

Yet the ecosystem didn’t grind to a halt. Other ants stepped in, taking over the roles of the removed species. “Insects are everywhere and some people question what all these species do in ecosystems,” said study lead author and JCU entomologist Dr. Peter Yeeles.

“Here, the research is showing that they provide a built-in redundancy that allows ecosystems to absorb shocks.”

“Think of them like pieces of scaffolding. Remove one, or a few, and the structure still stands because each part offers a degree of redundancy to the other parts. Redundancy makes systems resilient. Without it, even small disturbances can cause big collapses.”

The researchers observed that species richness increased in plots where dominant ants were suppressed. That increase contributed to higher overall multifunctionality.

This phenomenon, called functional redundancy, refers to the presence of species that perform similar ecological roles. If one species declines, others can maintain the system by doing the same job.

Ants fill gaps, but bring new risks

While the results initially appeared positive, a deeper look revealed hidden fragilities. The shift in species dynamics introduced new risks. As rare species filled the gaps, they brought with them specialization and less flexibility.

“Losing the common species can be like replacing a few reliable generalists with a team of specialists,” explained Dr. Yeeles.

“You might maintain performance, but you also increase the risk if one of them goes missing. With so much reliance on specific roles, losing any more species could cause much greater ecosystem damage than before.”

This change from generalist to specialist reliance may make ecosystems more efficient in the short term, but it reduces their capacity to recover from additional shocks. The safety net, once thick with backup options, becomes thinner with each lost species.

Some ant species boost functions

The experts tested four ant-driven ecosystem functions: granivory (seed eating), scavenging, plant protection, and myrmecochory (seed dispersal via ants). The researchers used experimental plots in southwestern Australia to measure how these functions changed when dominant ants were removed.

Interestingly, some functions improved in suppression plots. Granivory rates increased, and species richness was associated with better multifunctional performance.

But this came with caveats. For example, the function of plant protection significantly decreased, despite higher species richness. This was linked to the removal of ants known to deter herbivores on plants.

Contrasting effects on different functions revealed that gains in one area could mean losses in another. The balance of ecological tasks – what scientists call “multifunctionality” – became harder to maintain uniformly.

As functions became more dependent on fewer species, the entire system became more sensitive to further disruptions.

Hidden ant species step up

Another key finding of the study was that some ant species, previously minor players, became more ecologically important after dominant species were removed. These ants, once held back by competition, increased in abundance and performance. In some cases, they even enhanced specific functions.

This shift, however, was not random. Ants that had performed poorly in the presence of dominant species showed the greatest functional improvement in suppression zones.

According to the researchers, this suggests that the removed species had been suppressing the potential of the broader community. While the community as a whole stepped up, its structure was now fundamentally different — and more sensitive to future changes.

The phenomenon aligns with the concept of “low multifunctional redundancy.” In this view, species may overlap in one function but diverge in others. For example, an ant that disperses seeds may not be as good at scavenging.

Once the generalists disappear, specialists can’t always substitute across tasks. That leaves ecosystems reliant on unique species combinations that might be hard to replace.

Ants as ecosystem engineers

“It is easy to forget how important ants are in the majority of terrestrial ecosystems. They’re often referred to as ecosystem engineers because they have such profound effects on the ecosystems they live in,” said Dr. Yeeles.

“Some ant species are granivores, meaning they eat seeds, so they regulate plant communities.”

“For example, in an agricultural setting, ants consume weed seeds, providing free weed control services. They’re also important for soil structure as they dig and increase soil porosity to allow water infiltration. The list goes on.”

The study reinforces just how wide-reaching ant functions can be. Their activities influence plant growth, soil health, and nutrient cycling. Remove a key species, and subtle shifts occur that cascade through the ecosystem.

These shifts may go unnoticed at first, but they accumulate over time, reshaping entire habitats.

Looking at the bigger picture

“Globally, scientists are increasingly concerned about dramatic declines in insect populations, including many once-common species,” Dr. Yeeles warned.

“We must act now to protect not only rare species, but also the everyday insects that quietly keep our world running.”

The study serves as a wake-up call. Biodiversity loss is not just about rare or exotic creatures disappearing. It includes the steady erosion of common, hard-working species that form the foundation of ecosystem services.

These services – pollination, pest control, soil fertility – directly affect human food systems, clean water, and climate resilience.

This research moves the conversation beyond simply counting species. It asks us to consider what each species does, how they interact, and what happens when we take their presence for granted. Dominant ants are not just background characters. They are the gears of a complex biological machine.

Losing ant species weakens ecosystems

The study provides both hope and caution. Yes, ecosystems show an impressive ability to rebound when disrupted. But compensation is not the same as recovery. Each adjustment comes with trade-offs and increased fragility. Functional redundancy acts like insurance – but only up to a point.

As we continue to alter landscapes and apply pesticides, we must recognize the quiet work of ants and other insects. Protecting biodiversity means safeguarding not only the rare but also the reliable.

For nature to keep running smoothly, it needs all its workers – especially the ones we rarely notice.

The study is published in the journal Nature Ecology & Evolution.

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