Scientists have discovered a giant mushroom of unknown family in China.
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- Scientists have discovered a giant mushroom of unknown family in China.
In the forests of the Chinese province of Yunnan, scientists have discovered a previously unknown species of fungus Dianjunus rex, whose spore-bearing structures reach half a meter in height and weigh up to 2.2 kg. Genetic analysis has shown that the find represents an independent evolutionary line: for it, researchers have identified not only a new species and genus, but also a separate family. They dated its origin to about 65 million years ago. Why the mushroom got its "royal" name, how scientists determined the age of its evolutionary line, and why it might need such a large size are described in the Izvestia article.
A giant on the roots of an oak tree
An unusual mushroom was found during field research in different areas of Yunnan. The scientists examined temperate coniferous forests near Damaidi and Yipinglan, as well as a tropical rain forest in the Nanban area. Large whitish formations grew on the woody roots of the Chinese cork oak and protruded from the root zone. The researchers determined that in front of them was an unknown representative of marsupial fungi, or ascomycetes.
The detected structures are called stromas. They contain formations involved in the formation of spores. In D-rex, these structures grow vertically and reach unusual sizes for their group. According to the authors, the stromas of Dianjunus rex are the largest documented spore—bearing structures of ascomycetes. Previously known tall representatives of this group reached about 20-30 cm, while the new find grows up to 50 cm.
We are talking about a record among marsupial mushrooms. These measurements characterize the visible spore-bearing structure, rather than the size of the entire mycelium, so it would be incorrect to consider D-rex the largest fungal organism on the planet.
Why was a new family needed?
To determine the position of the find in the mushroom system, scientists did not limit themselves to its appearance. The collected samples were transferred to the collection of the Kunming Institute of Botany, and the spores were grown on nutrient media to study the development and structure of the fungus.
The researchers also sequenced his genome. The morphological features, sequences of several genetic markers, and genome analysis data were compared. This combination of methods made it possible to determine the kinship of an unusual organism.
The results showed that Dianjunus rex differs from the known fungi significantly enough to separate it into an independent genus Dianjunus and a new family Dianjunaceae in the order Xylariales.
"This remarkable species represents a new family of fungi, Dianjunaceae, and provides a rare opportunity to study the evolution of unusually large fungal body forms," said Indunil Senanayake, researcher at the Wild Species Genetic Resources Bank at the Kunming Institute of Botany and corresponding author.
The closest known relative of the find turned out to be Graphostroma platystoma. This fungus is found on the dead wood of deciduous trees in the Northern Hemisphere. However, the similarity of origin does not negate the differences that led the researchers to classify D-rex as a separate family.
Where did the name D-rex come from?
The name Dianjunus rex refers both to the local history and the size of the mushroom. The first part is related to the ancient kingdom of Dian, and the Latin rex means "king". So the authors emphasized the unusual appearance of the find and its origin.
The research report also uses the abbreviated name D-rex. It is consonant with the well-known T. rex, but the connection of the discovery with the age of dinosaurs lies primarily in the estimated date of its evolutionary lineage. The new species has not been found in a fossil state. Scientists have studied a modern mushroom, and information about the ancient origin of its family was obtained by analyzing genetic data.
The evolutionary line is 65 million years old
To estimate the time of occurrence of Dianjunaceae, the researchers used the molecular clock method. It allows us to estimate the timing of the divergence of evolutionary lines based on accumulated genetic differences, taking into account time benchmarks.
A comparison of the data of the new fungus with the genomes of other representatives of the kingdom allowed us to attribute the origin of the family to about the beginning of the Paleocene, about 65 million years ago. This is about a million years later than the Cretaceous-Paleogene mass extinction, which occurred about 66 million years ago. Then the non-avian dinosaurs and many other animals and plants disappeared.
This sequence of events interested the authors. After the mass extinction, forest ecosystems were rebuilt, and the abundance of dead plant material could create favorable conditions for organisms associated with the decomposition of wood.
"After the mass extinction, forests experienced drastic changes, including the sudden appearance of large amounts of dead plant material. For wood—decomposing fungi, such environmental changes could open up new ecological opportunities," Senanayake explained.
However, the timing does not prove that it was the mass extinction that led to the emergence of Dianjunaceae. The authors suggest a possible explanation that needs to be verified. In addition, the estimate of 65 million years refers to the divergence of the evolutionary line of the family, and not to the age of the modern species or the specimens found.
Why would a mushroom grow to half a meter
Researchers suggest that height may contribute to the spread of spores. The stroma, towering above the surrounding vegetation and forest litter, potentially receives better conditions for their transport by air currents.
"The fruit body, towering above the surrounding vegetation and litter, could spread the spores more efficiently with the help of wind in dense forests," Senanayake suggested.
At the same time, the formation of a large structure requires significant energy costs. According to the researcher, this method of reproduction could gain a foothold only where the advantages compensated for the consumption of resources. So far, this is a hypothesis about a possible function of giant stromes. Their sizes have been measured, but the advantage in the spread of spores still needs to be confirmed by separate studies.
The authors also pay attention to the properties of other representatives of Xylariales. Many of them produce enzymes capable of breaking down complex plant substances. Similar mechanisms can help the D-rex use dead wood, but the features of its diet require further study.
Why the large mushroom remained unknown for a long time
The finding shows that even a noticeable-sized organism can remain without a scientific description for a long time. According to Senanayake, the fungal diversity of East Asian forests is still poorly understood.
Field research is complicated by the inaccessibility of individual territories. In addition, the appearance of spore-bearing structures may depend on the season, and some fungi are difficult to detect during a routine forest survey. Historically, the attention of scientists has also been more often attracted by species of obvious economic importance.
At the same time, the diversity of natural conditions and interactions between organisms makes the forests of the region a promising place for new discoveries.
"The discovery shows how much diversity of fungi in the forests of East Asia has yet to be studied," Senanayake said.
Dianjunus rex expands the understanding of the possible size of marsupial fungi and adds a new branch to their evolutionary tree. The following studies should help to find out how widespread it is, how it interacts with trees, and what conditions allowed its unusual spore-bearing structures to form.
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