Where Did Plants Originate and How Did They Spread? Unraveling the Footprints of Plant Distribution Through Science
Dr. Noriyuki Fujii
Associate Professor, Facility of Advanced Science and Technology
A Phylogenetic Tree Built from Genetic Sequences Reveals the Origins and Distribution of Plants
Interviewer: Your research focuses on plant studies, correct?
Yes, I am conducting research to uncover how the plant flora in Japan and surrounding East Asia was formed. Flora is essentially a list of plant species that make up a particular region’s vegetation. In Japan, there are about 5,000 plant species, and I am investigating how they arrived and spread across the country using DNA analysis. However, since it is impossible to study all plants, my research focuses on three specific groups: alpine plants, Mansen elements, and Sohayaki elements.
Q: Alpine plants are familiar, but the terms “Mansen elements” and “Sohayaki elements” are less commonly heard. What do they refer to?
Alpine plants are believed to have migrated to Japan from the north, including the arctic region. Mansen elements refer to plants that are thought to have traveled from the region of China known in ancient times as “Manchuria,” a continent located to the west of Japan, through the Korean Peninsula, before reaching Japan. Sohayaki elements, on the other hand, are plants that are believed to have arrived in Japan in ancient times, before the Japanese archipelago separated from the continent.
However, there have been few studies that thoroughly verify whether these plants actually migrated from the north or the continent. Recent research has even revealed that some plants originated in Japan and then spread to other countries. I think that even among the plants generally believed to have come from the north or the continent, there may be some that need to be reconsidered in terms of their origin and distribution.
Photo: Kisumire (Viola orientalis): A symbol of Spring in Aso and a representative species of the Mansen elements.
Interviewer: Please tell us about what you have discovered so far.
One of my research subjects is Kisumire (Viola orientalis). In Aso, this plant blooms in bright yellow clusters after the traditional grassland burning, and it is classified as the Mansen elements.
To investigate its evolutionaly history, I analyzed the genes of Kisumire populations from its core habitats, Northeastern China, the Russian Far East, the Korean Peninsula, and the Japanese archipelago. Using this data, I constructed a phylogenetic tree.
A phylogenetic tree is a method used to trace the evolutionary relationships and origins of species based on genetic data. It functions like a family tree for plants: samples are collected from wild populations in different regions, and their genetic sequences are analyzed to determine evolutionary relationships. If a population’s DNA sequence appears at the base (the earliest branching point) of the tree, that location is considered the plant’s place of origin. In the case of Kisumire, the phylogenetic tree showed that the earliest branches were occupied by populations from Russia and other continental regions, while Japanese populations were the outermost tips. This confirms that Kisumire originated on the continent and later spread to Japan. We have published these findings in a paper.
Figure: Phylogenetic Tree of Kisumire at the Individual and Population Levels.
Entered the Faculty of Engineering, but transferred to the Faculty of Science
The Encounters with my teachers and specimens are connected to the present day
Interviewer: What inspired you to pursue plant research?I originally entered the Faculty of Engineering at Shinshu University. However, I had always loved the stars, and I joined a natural history club where many members were passionate about plants, insects and animals. Through this club, I started thinking about mastering plants. Living in nature-rich Shinshu, I set a personal goal to see every plant in the region, constantly comparing them with pictorial books. That was the start of my plant research. As my interests shifted, I took the transfer exam and moved to the Faculty of Science. There, I met the late Professor Tatemi Shimizu, a renowned botanist. Wanting to continue learning from him, I followed him to Kanazawa University, where I eventually obtained my degree.
Interviewer: Your collection of plant specimens is remarkable, and they all look beautifully preserved!
After obtaining my degree, I started working at the Makino Herbarium at Tokyo Metropolitan University. The Makino Herbarium holds a huge collection of plant specimens, including the “Makino Collection” created by Dr. Tomitaro Makino, regarded as the father of Japanese plant taxonomy. I spent about 10 years there, working closely with plant specimens.
A crucial aspect of a specimen is its label, which records where, by whom, and when it was collected. Without this information, it is nothing more than a pressed flower. The label ensures specimen serves as solid scientific evidence. Each specimen holds valuable information, not only about the plant’s leaves and flowers but also about its flowering period, distribution in Japan and the continent, and broader natural history insights. By accumulating such specimens, we can determine how many species exist worldwide and where they are distributed. For instance, the Makino Herbarium has specimens of wild Japanese primrose (Primula sieboldii) collected in Tokyo. While the wild Japanese primrose are now extinct in Tokyo, but the specimens are proof that the plants once thrived there. Plant specimens hold a wide range of scientific and historical value.
Photo: A plant specimen of Tsuchiguri (Potentilla discolor) prepared by Associate Professor Fujii, collected in Kato-shi, Hyogo Prefecture in May 2018
Protecting Rare Plants That Are Disappearing Along with Grasslands
Contributing to the Preservation of Aso’s Grasslands Through Research
Interviewer: I heard that your research also contributes to the maintenance and restoration of Aso’s grasslands.Yes, about 100 years ago, in the Taisho era, Aso’s grasslands covered about 70,000 hectares, but today, only 15,000 hectares remain. As the grasslands shrink, many grassland plants are facing extinction. According to the Ministry of the Environment's Red Data Book, 70 to 80 species of Aso's grassland plants are currently listed on the book.
To support grassland restoration, we conducted research on a National Trust site owned by the certified NPO “Aso flower field association” in Takamori Town. The initiative involves restoring about 10 hectares of former cedar forest back into grassland. We conduct annual controlled burns and monitor vegetation changes. Specifically, we record the plant species in 2-squre-meter sections, noting their proportion and height in both spring and summer. Our students work had to collect this data under the scorching sun.
Right after the cedar trees were cut down, non-native plants like Tall goldenrod (Solidago altissima) spread rapidly, which initially raised concerns. However, after four to five years, native grassland plants like Japanese silver grass (Miscanthus sinensis) began to dominate. This is because controlled burns eliminate invasive species, whereas native grassland plants store nutrients underground, allowing them to survive and regenerate. Our ultimate goal is to restore a biodiverse "hayfield" and establish a sustainable system to maintain it. We are now in the 12th year of this project, and we are getting closer to our ideal state of a biodiversity-rich hayfield.
Photo: The grasslands of Aso’s northern outer rim. The scatted red flowers are Ogura-sennou (Silene kiusiana)
Interviewer: I am delighted that Aso is the focus of your research.
I have been working at Kumamoto University for 20 years now, and I have encountered many plant species that exist only in Aso. However, as the grasslands decline, these plants are disappearing as well, and I feel a strong desire to protect them. One way to do that is by preserving the grasslands themselves. I want to find an efficient method to restore them.
Speaking of Aso, the wild Suzuran (wild lily of the valley; Convallaria majalis var. manshurica) that grows in Aso-shi Namino-town is particularly fascinating. In Kyushu, this species is found only in a small area of Namino. There are large populations of wild Suzuran in the central Honshu and Hokkaido, it has been assumed that the Suzuran in Namino also originated from the north. However, since there are also wild populations in the Korean Peninsula, it is possible that they may have arrived from the west instead. I am interested in identifying the origins of such isolated plant populations.
Now we can use more molecular data, allowing us to conduct detailed analyses. We hope to study at least 10 more species belonging to the Mansen elements and write papers about them. Beyond that, I also want to reconsider what Mansen elements actually are, because the definition is somewhat unclear. Exploring and refining this concept is another challenge I would like to take on.
Related Links: