The Extraordinary Wollemi Pine: Nature's Astonishing Creation
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| The Endangered Wollemi Pine: A Living Fossil Facing Ancient Challenges |
With a scarcity of living relatives and a lineage stretching back to the time of dinosaurs, the Wollemi pine (Wollemia nobilis) has often been referred to as a "living fossil." Recently, botanists have successfully sequenced the genome of the Wollemi pine, shedding light on how this plant has remained remarkably unchanged for millions of years.
Initially thought to be extinct, the remarkable discovery of this unique tree occurred in 1994 when a group of hikers stumbled upon it while exploring a canyon in the northwest of Sydney. Today, fewer than 60 of these plants are known to exist in the wild, confined to a mere 10 square kilometers (3.8 square miles) in the same region. Unfortunately, this small population is under constant threat from the wildfires that frequently sweep through the area during dry months.
In a preprint paper, yet to undergo peer review, an international team of researchers elucidates how the Wollemi pine's minuscule population has led to extensive inbreeding. This phenomenon is a result of the plant's massive genome, comprising 26 chromosomes with approximately 12.2 billion base pairs, in stark contrast to the human genome's roughly 3.4 billion base pairs. Despite this immense genome size, the species exhibits remarkably low genetic diversity.
By delving into this wealth of genetic information, the researchers have pieced together a glimpse into how the Wollemi pine has endured, flourished, and declined over countless millennia. Apparently, the tree's population experienced rapid growth around 8 to 6 million years ago during a period of overall drying as Sahul, a landmass connecting present-day Australia, Tasmania, New Guinea, and the Aru Islands, moved northward.
The study authors suggest, "During this time, rainforest retreat and the expansion of open forest may have created a niche for an emergent such as Wollemia to expand its range."
However, as the rainforests receded further, the population dwindled to just one-fifth of its original size between 7 to 3 million years ago. It has been confined to its relatively small Australian habitat since the last significant glacial and drying period on the continent approximately 120,000 years ago, marked by widespread aridity and intensified wildfires.
While this research primarily delves into the ancient history of the Wollemi pine, it carries concerning implications for its future. The pine's genome unequivocally illustrates that its population declines when conditions become hotter and drier, primarily rendering its habitat more susceptible to wildfires.
As witnessed during the unprecedented bushfires of 2019, the climate crisis is already exerting immense pressure on Australia's forest ecosystems. With temperatures projected to rise further, the fate of the dwindling Wollemi pine population remains uncertain.
The study authors conclude, "Our population genomic analysis has revealed the highly inbred, and likely clonal relationship of the few remaining wild Wollemi pines consistent with their critically endangered status. This analysis has revealed reductions in population size that coincided with drier and warmer climates over geological time. This trend has rapidly accelerated in recent years in the face of man-made climate change, as sharply illustrated by the recent destructive bushfires that took a toll on the remaining stands."
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