These ferns may be the first plants known to work together as ants do

Question

In this article, the author discusses a discovery made by Kevin Burns about staghorn ferns. Kevin Burns is a biologist, meaning that he studies living things.
A mass of strange ferns embraces a trunk high among the treetops. They look like a giant tangle of floppy, green antlers. Below their fork-shaped fronds and closer into the core of this lush knot of greenery are brown, disc-shaped plants. These, too, are ferns. They are even the same species. Together these individuals form a society, a type of society that has only ever been observed in animals, especially bees, termites, and ants. Staghorn ferns — and possibly other plants — appear to work together, each taking on different tasks that together aid their society.

Kevin Burns is a biologist at Victoria University of Wellington in New Zealand. He first became familiar with the ferns while working on Lord Howe, an isolated island between Australia and New Zealand. He took notes on local island epiphytes (EP-ih-fytes) — plants that grow on other plants — and one species caught his eye: the staghorn fern. The staghorn fern (Platycerium bifurcatum) is native to parts of mainland Australia and Indonesia, too.

“I realized,” Burns recalls, these ferns “never occur alone.” Some of the larger clusters were massive. They contained hundreds of individuals, and Burns soon realized “each one of those individuals was doing a different thing.”

He likens the fern colonies to an upside-down umbrella. Some with long, green, waxy “strap” fronds appeared to direct rainwater to the center of the clump. There, spongey, disc-shaped, brown “nest” fronds absorbed this moisture.

The whole community reminded Burns of a termite mound, which houses a shared store of resources. Inside it, various members of the termite colony perform different tasks.

Scientists call such cooperative groups eusocial (Yu-SOH-shul). Overlapping generations live together in castes,1 with each performing different roles. Among eusocial animals, some workers might be responsible for finding food, while others might be nurses or caregivers.

Eusocial has been used to describe certain societies of insects and crustaceans, along with two species of mole rats. Burns wondered if ferns, too, might be eusocial.

His team’s data now indicate they are. These ferns appear to form a complex society made up of interdependent groups.

Truly eusocial? Let me count the ways
Ferns reproduce via spores, which form on the underside of leaf-like fronds. Some four in every 10 fronds of the studied communities of staghorn ferns could not reproduce and mostly served as nests for others. However, another fern with strap fronds could develop fertile spores. This suggests a division of labor between fronds that do and don’t form nests.

Tests also revealed that nest fronds sop up more water than strap fronds do. Earlier studies conducted by other scientists had found networks of roots running throughout the colony. Using them, nest fronds can share their water, slaking the thirst of neighboring strap fronds.

Burns and his coworkers also analyzed the genes in 10 staghorn colonies on Lord Howe Island. Eight hosted genetically identical individuals, while only two colonies contained individuals whose genetics differed. Such a high degree of genetic relatedness is seen in colonies of eusocial insects. In ants and bees, for instance, many sisters contribute to the survival of their home nest.

Burns thinks the staghorns’ newfound traits fulfill many of the requirements needed to support a claim that they, too, are eusocial.

Looking at epiphytes as eusocial is “really cool,” says Michelle Spicer, an ecologist at the University of Puget Sound in Washington.

To Burns, the division of labor to build shared resources “appears to be a key feature that sets staghorn [ferns] apart from other colonial plants.” A stressful life in the treetops — far from the soil — may have helped the ferns develop eusocial traits, Burns says. The society these plants create allows all members to share scarce supplies of water and nutrients. Spicer points out, however, that a sharing of water and nutrients also occurs among other epiphytes.

The new study makes a compelling case that staghorn ferns are eusocial, says Brian Whyte. “The epiphyte lifestyle certainly facilitates2 group living,” he adds. “And group living is where all social stories start.” Whyte is a biologist at the University of California, Berkeley.

Whyte is fascinated by how staghorns form colonies in the wild, where members perform different, individual tasks. However, he notes, when grown in soil as ornamental plants, these ferns don’t need a community. They now form individual strap fronds. Such variability is not typical of eusocial species, he says.

Burns says he’s really excited to have found something in the wild that unexpectedly turns out to be “comparable to some of the coolest, most advanced societies in the living world.” And regardless of how eusocial these ferns are, they still have intriguing similarities and differences from caste-forming animals, he adds.

Answer 1

The article discusses an exciting discovery by biologist Kevin Burns about staghorn ferns (Platycerium bifurcatum), which may exhibit eusocial behavior similar to that found in certain animal societies like ants, bees, and termites. Burns observed that these ferns, particularly on Lord Howe Island, form large colonies that work together in a coordinated manner, suggesting a division of labor among different individuals within the colony.

The physical structure of the fern colonies resembles an upside-down umbrella, with two types of fronds – the long, green "strap" fronds that direct rainwater and the brown "nest" fronds that absorb this moisture. Burns notes that many fronds do not reproduce and instead serve as nests for other fronds, showcasing the community’s interdependence. This arrangement resembles eusocial groups where individuals perform specific roles, such as foraging or caregiving, to support the colony.

Burns and his team conducted genetic analyses and found that a significant number of fronds within these colonies were genetically identical, a trait common in eusocial insects. These findings led them to propose that staghorn ferns possess traits that align with eusocial behavior, including cooperation and resource sharing, which are typically seen in social insects.

Despite these similarities, there are key differences noted by researchers. For example, when staghorn ferns are cultivated in soil as ornamental plants, they do not exhibit the same community behaviors, instead growing as individuals. This indicates that environmental pressures, such as the need for cooperation in the treetop ecosystem, may have influenced the development of eusocial traits in staghorn ferns.

The implications of this discovery are significant, as they challenge traditional understandings of eusocial behaviors and highlight the complexity of plant interactions. Researchers are intrigued by the possibility that other plant species may also exhibit similar social structures, expanding the concept of eusociality beyond animals to include the plant kingdom. Overall, the findings suggest that the study of plant behaviors and relationships is a valuable field that merits further exploration.