Borneo is home to more than 300 species of palm, but one of them has remained unnoticed by scientists until recently.
Pinanga subterranea, as its name suggests, is a palm that produces its flowers and fruits almost entirely underground.
This remarkable adaptation makes it the only known member of the palm family (Arecaceae) to display such behaviour.
A paradoxical reproductive strategy
David McNew/Getty Images for Lumix
Flowering and fruiting underground (geoflory and geocarpy) are very rare and seemingly paradoxical reproductive strategies among flowering plants (angiosperms), as per Phys.org.
Most plants develop their flowers and fruits above ground, facilitating pollination and seed dispersal.
However, some plants have evolved to produce their reproductive organs below the soil surface, which may offer some advantages in harsh environments, such as protection from heat, drought, and herbivory.
Geoflory and geocarpy can take different forms. Some plants, such as the Australian underground orchids (Rhizanthella spp.), flower, and fruit exclusively below ground.
Others, such as the peanut (Arachis hypogaea), flower above ground but bury their fertilized flowers and fruits underground.
Some plants, such as Commelina benghalensis, produce two sets of flowers and fruits, one above and one below ground.
Although geoflory and geocarpy are widely scattered across the angiosperms, occurring in at least 33 plant families, 89 genera, and 171 species, they have never been reported in palms until now.
Pinanga subterranea is the first palm species to be described that flowers and fruits almost entirely underground.
Pinanga subterranea is native to the tropical island of Borneo in Southeast Asia, where it can be found scattered across the primary rainforests of western Borneo, crossing state lines from Sarawak in Malaysia to Kalimantan in Indonesia, as per TDPel Media.
The plant is well-known to locals who like to snack on its bright-red fruit -a sweet and juicy delicacy consumed in some parts of the island.
However, until now, the plant has remained unnoticed by scientists who have described around 300 different species of palm on the island.
The plant was first brought to the attention of researchers by Dr. Paul Chai, a Malaysian botanist and namesake of the palm species Pinanga chaiana.
He encountered the plant in 1997 during a visit to Lanjak Entimau Wildlife Sanctuary, Sarawak.
He noticed the fruit that had been revealed when he brushed aside the thick leaf litter surrounding a young palm.
In 2018, researchers from the Royal Botanic Gardens (RBG), Kew and partners revisited the site and collected several specimens of the palm for scientific research.
Dr. Benedikt Kuhnhäuser, Future Leader Fellow at RBG Kew, said: "Without the tip-off from our Malaysian colleague Dr. Paul Chai, we probably would have mistaken this exciting new species for an unremarkable palm seedling and would have walked right past it."
A fascinating enigma for science
The discovery and description of Pinanga subterranea as a new species to science are remarkable for several reasons.
First, it adds to the diversity and conservation value of Borneo's rich flora, which is under threat from deforestation and habitat loss.
Second, it raises many questions about the evolution, pollination and dispersal of this unusual palm species.
How did Pinanga subterranea evolve to flower and fruit underground? What are the benefits and costs of this adaptation? How does it get pollinated? What animals disperse its seeds? How widespread and abundant is it? These are some of the questions that researchers hope to answer in future studies
Dr. William Baker, Head of Palm Research at RBG Kew, says: "Pinanga subterranea is a fascinating enigma for science. It challenges our understanding of how plants reproduce and how they interact with their environment. It also shows how much we still have to learn about Borneo's biodiversity."
