A new plant's name that tells a story

Fairy lanterns, or Thismiaceae as they are known to botany, are very unusual plants found mainly in tropical but also in subtropical and temperate regions. First of all, they are not green and do not engage in photosynthesis, but rather feed on fungal mycelia in the ground. As a consequence, they are often hidden under fallen leaves and only for a brief period produce above-ground flowers that look like glasswork. The Japanese name for Thismia, one of the major groups within this family, is "Tanuki-no-shokudai," which means "raccoon dog's candleholder" and refers both to their shape and their underground lifestyle. However, they are also extremely rare and difficult to find. "At present, approximately 100 species within the family have been identified, nearly half of which are known only from their first discovery, sometimes from a single specimen," explains Kobe University botanist SUETSUGU Kenji, who is an internationally renowned expert on non-photosynthetic plants.

Suetsugu has long-standing collaborations with local botanists who have access to secluded areas all over Japan. He says, "The dedication of Japanese amateur researchers to revealing the hidden flora of these regions has been crucial in identifying species unknown to science." And so, when he was sent a specimen of a fairy lantern that a hobby botanist had found and that a local expert thought represented a new species of the genus of Tanuki-no-shokudai, he knew he had to investigate. However, it soon became clear "that this plant was not included in any of the existing genera (such as Thismia) because of its unique features, and it became necessary to obtain additional individuals for further examination." So, he went to Kimotsuki in Kagoshima Prefecture, where the discovery had been made, but could not find any other samples. However, a year later he tried again and got lucky: They found four more plants, all in the same narrow area.

The Kobe University expert now published his analysis in the scientific Journal of Plant Research. Based both on morphological and genetic analysis, the team concluded that the plant is not only a new species, but in fact different enough from Tanuki-no-shokudai to be a different genus -- the next level of relationship above species. The researchers think the plant probably diverged at an early stage in the evolution of the whole Thismiaceae family and retains characteristics that are common to the family but have been lost in the Thismia genus. This is the reason Suetsugu chose the name "Mujina-no-shokudai," or "badger's candleholder": "Mujina" is an old Japanese word for a badger, but sometimes has also been used for the raccoon dog which it resembles but is different from. Thus, the name reflects the plant's relationship with Thismia. The Latin name Relictithismia kimotsukiensis is similar, as it can be translated as "Thismia relict of Kimotsuki."

"Japan is one of the regions in the world where botanical surveys are most advanced, making the discovery of new plant species extremely rare, and the discovery of a new genus even more so," says Suetsugu. In fact, the last discovery of a new vascular plant concurrently identified as a separate genus was the discovery of Japonolirion in 1930, almost 100 years ago. Suetsugu explains, "This research might suggest that many other new species may be hiding in regions previously thought to be well-studied and underscores the critical need for ongoing exploration and investigation of the planet's flora both abroad and at home."

A plant that feeds on fungi and is so limited in its local spread is also exceptionally vulnerable to environmental change. This motivates Suetsugu to deepen his research, saying, "A segment of our future research will be dedicated to ecological studies aimed at deciphering the interactions between Relictithismia and its fungal hosts, in addition to assessing the impact of environmental alterations on these associations."

This study was supported by the PRESTO program (grant JPMJPR21D6) of the Japan Science and Technology Agency, the JSPS KAKENHI (grant 21K06307) and the Environment Research and Technology Development Fund (grant JPMEERF20204001) of the Ministry of the Environment, Japan. It was conducted in collaboration with an independent researcher and researchers from Kyoto University and the Kagoshima University Museum.