This parasitic plant’s survival may depend on a rare rabbit

This parasitic plant’s survival may depend on a rare rabbit

On a small chain of islands off the coast of Japan, local biologists found a peculiar bite mark Balanophora yuwanensis plant, plant. They hypothesized that the toothy impression might belong to the Amami rabbit, a fierce and dark-haired nocturnal creature named for the Amami Islands. The rabbit evolved separately on the islands, making it genetically distinct from other species in Japan. So the team set up infrared-triggered cameras nearby B. yuwanensis, a non-photosynthetic plant, and spent 52 days observing which animals eat it.

Their guess was correct: of all the animals in the forest, the Amami rabbit ate fruits grown on the Amami B. yuwanensis plant the most. The team’s observations were later confirmed when they examined the rabbit’s feces. The Kobe University paper was published in the journal ecology on Monday. In addition, the researchers discovered that the rabbit could be critical to the plant’s survival. After eating the fruit, the Amami rabbit poops out the seeds and disperses them throughout the island’s subtropical evergreen forests.

Seed dispersal by animals is particularly important for the B. yuwanensis plant, plant. Although the plant’s seeds are small, they are unlikely to be dispersal by the wind because the plants grow under the canopy that blocks strong winds, explains Kenji Suetsugu, lead author of the study and a professor at Kobe University.

a Balanophora yuwanensis plant, which are red spherical bulbs with ruffled little bumps.  on the right are the eaten plants
Each round mass of Balanophora yuwanensis looks like a single fruit but consists of several thousand fruits, each about 0.3 mm in size. The clusters consist of numerous red bumps that are not the fruit but modified leaves that hide the actual fruit underneath. Yohei Tashiro

The amami rabbit’s curious role in the spread of the plant is reinforced by the fact that B. yuwanensis is no ordinary plant. It has neither roots nor leaves and with its dark red-brown color it resembles a strawberry more than the traditional leaf shoot. It cannot photosynthesize, so it acts as a parasite, attaching itself to the roots of other plants to gather nutrients. And it doesn’t produce fleshy fruits, which have bright colors, juicy textures, and distinct smells that attract seed-dispersing animals looking for a snack. Instead, the parasitic plant produces dried fruit – but the Amami rabbit still eats it. And after the rabbit has had enough of those fruits, it digs underground burrows where it defecates, which could help place the seeds near the roots of compatible host plants B. yuwanensis.

The latest findings also highlight the complex relationship between animals and the services they provide to their environment. “The rabbits probably form a crucial connection between them [B. yuwanensis] and its hosts,” Suetsugu wrote in an email interview popular science. “Such natural history observations expand our understanding of ecosystems enormously.”

Evan Fricke, an ecologist at the University of Maryland who studies seed dispersal, adds that the study highlights the sometimes unexpected role species play in maintaining the web of life. “I feel like there’s a growing recognition that more plant species depend on animals for seed dispersal than previously thought, even if they don’t have physical structures like pulp to attract fruit-eating animals or hooks to attach to animal fur. ‘ wrote Fricke in a statement PopSci.

The research team’s infrared images of an Amami rabbit voraciously feeding on a non-photosynthetic plant. Credit: Kenji Suetsugu

Locals have tried to protect the Amami rabbit, which many consider the islands’ cultural symbol, says Suetsugu. In recent years, the rabbit has also been used to promote tourism. But increasing habitat destruction in the Amami Islands has left both the Amami rabbit and the Amami rabbits behind B. yuwanensis Plant endangered, says Suetsugu. The government has made some efforts to protect the species from extinction, including hunting the rabbit, mongoose and wildcat predators, which have yielded some positive results.

Still, scientists have yet to discover any services that endangered animals might provide to their ecosystems, Suetsugu says. Their declining population size or extinction could significantly affect how ecosystems function.

“Many endangered species have not yet been fully studied and their full ecological importance may not yet be known,” Suetsugu wrote. “Endangered species can, for example, play an important role as pollinators, seed dispersers, predators or prey. They can also help maintain the balance of an ecosystem by controlling the populations of other species.”

[Related: The curious case of an endangered wildcat and a disappearing fruit tree]

Scientists are still trying to understand the role of endangered animals in their ecosystems, including in seed dispersal, Therese Lamperty, a postdoctoral researcher at the University of Washington, said in a statement PopSci. The study describes a compelling example of pursuing a subtle field observation to make a novel discovery, she says.

“Because many endangered animals share common traits, such as large body sizes, they tend to be species that also play unique or relatively influential roles in their ecosystems,” Lamperty wrote. “But as the existing data is limited, we cannot say for sure and more research is needed.”

Suetsugu says the unknown functions of endangered species should be considered when governments take conservation measures. Understanding the role of endangered species can help conservation managers more effectively protect and restore habitats, control invasive species, and reduce other threats, he says.

“Protecting endangered species not only helps preserve biodiversity, but can also have important benefits for human well-being,” says Suetsugu.

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