Long known as "living fossils" from the dinosaur era due to their highly conserved physical forms since the Jurassic period, Cyatheaceae tree ferns have puzzled scientists for decades: How have these ancient plants survived mass extinctions and environmental upheavals while retaining their stable appearances, yet still evolving into diverse species?

To address this knowledge gap, a research team from the South China Botanical Garden of the Chinese Academy of Sciences, has conducted a study and revealed that a single genome duplication event 154 million years ago—and subsequent genetic adaptations—enabled the ferns' remarkable resilience. Their findings were recently published in Molecular Biology and Evolution.

Using advanced comparative genomics and transcriptomics, the researchers analyzed high-quality genome sequences of multiple Cyatheaceae ecotypes, including both tree-forming varieties (with thick trunks) and non-arboreal types (lacking significant stems).

The researchers discovered that despite slow overall molecular evolution, all Cyatheaceae lineages share a single whole-genome duplication (WGD) event dating to the late Jurassic. This genetic "copying" provided two critical advantages: it helped ancient tree ferns survive environmental crises of that era, and laid the genetic groundwork for the group's later species diversification.

Tree-forming species, for example, retained WGD-derived genes linked to cell wall synthesis and lignification—strengthening their trunks for structural support. In contrast, non-arboreal species kept more genes related to metabolism and defense, boosting their ability to thrive in harsh conditions.

In addition, the ferns' seemingly unchanging morphology masks active genomic evolution. Frequent bursts of transposable elements drove major changes in genome structure, including variations in genome size and chromosomal rearrangements. These changes acted as an engine for rapid local evolution, even as the plants' overall shape stayed the same.

The team also found that the evolution of tree-like forms depended not just on WGD-retained genes, but on complex transcriptional regulation. This mechanism allows the ferns to coordinate lignin production with light-sensing abilities—helping them adapt to grow under the canopies of angiosperms, which now dominate most ecosystems.

This study redefines "evolutionary stasis" in living fossil plants as genomic dynamic equilibrium. Genome plasticity and local innovation, combined with evolutionary conservatism, have enabled tree ferns to persist for hundreds of millions of years.

This study not only provides crucial genomic resources for conserving rare Cyatheaceae "living fossil" ferns but also establishes a novel theoretical framework by outlining key mechanisms that underpin the long-term survival and evolution of ancient relict plants, the researchers noted.