Abstract:
Researchers discovered and named a giant fungus, Dianjunus rex, nicknamed "D-rex" in the forests of Yunnan, China. The upright fruiting bodies it grows can reach up to 50 centimeters, each weighing 2.2 kilograms. They are the largest fruiting bodies currently known in the Ascomycota; the previous record of this kind was about 20 to 30 centimeters.
The research team collected samples from barley fields in Lijiang, Yunnan, temperate coniferous forests near Yipinglang, and tropical rainforests near Lampang. These pale white structures grow from near the woody roots of the Chinese cork oak. Combining morphological observation, multi-gene phylogenetic analysis and genomic data, the team confirmed that it belongs to a new species and new genus in the order Dianjunaceae, and established a new family "Dianjunaceae" accordingly.
The researchers used a "molecular clock" to compare the genomes of D-rex and hundreds of fungi, and estimated that the origin of the family Yunnanaceae was about 65 million years ago. The time range was estimated to be 50 million to 80 million years ago, close to the end of the Cretaceous-Paleogene mass extinction. Researchers propose that changes in forest ecology and an increase in dead plant material after the mass extinction may bring new ecological opportunities for wood-decomposing fungi; this is still a hypothesis based on time correlation and cannot prove that the extinction event directly contributed to the emergence of the fungus.
Why D-rex grows such huge reproductive structures has not yet been determined. The research team speculates that the fruiting body, which is higher than the surrounding vegetation and litter, may help it spread the spores by wind in the dense forest; however, building such a large structure also requires a large amount of energy.
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