Jake Buehler
2021
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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.
How does the author develop his claim that staghorn ferns are most likely eusocial?
A. by discussing plants other than staghorn ferns that are eusocial
B. by describing how certain traits of eusocial organisms apply to staghorn ferns
C. by explaining how staghorn ferns have changed over time to become eusocial
D. by suggesting that most plants are eusocial
11 answers
The correct answer is B. by describing how certain traits of eusocial organisms apply to staghorn ferns.
The author discusses specific characteristics and behaviors of staghorn ferns that align with the definition of eusociality, such as division of labor, genetic relatedness, and cooperative water sharing, thereby building a case for their eusociality.
The meaning of "variability" in paragraph 16 is A. changeability.
In the context of the paragraph, it refers to the differences in how the staghorn ferns behave when grown in soil versus in their natural environment, highlighting the potential for change in their structure and function based on different growing conditions.
The best answer that identifies the author's main purpose in the article is B. to share findings that support the idea that staghorn ferns are eusocial.
The article focuses on presenting the research and observations made by Kevin Burns and his team, which suggest that staghorn ferns exhibit eusocial traits, thereby supporting the idea of their eusociality.
The two statements that best describe the central ideas of the article are:
C. Magpies that trust people can form long-lasting friendships with them.
D. People can establish a friendship with magpies by offering them food.
These statements highlight the relationship between magpies and people, focusing on trust and friendship developed through specific behaviors.
The correct answer is C. presenting the question she plans to answer throughout the article.
The author typically introduces a topic by posing a question or establishing a focus that guides the discussion, particularly regarding magpies and their behavior in relation to humans.
The correct answer is D. distinguishing between what does and does not qualify as a friendship between birds and humans.
In paragraph 3, the author clarifies that while many bird species can become tame enough to take food from humans, this behavior does not constitute true "friendship." The author emphasizes the unique bond that can develop between magpies and people, which is more meaningful than simply accepting food.
