Cloning the ice age gum tree to save its last wild plants

In a Canberra glasshouse, horticulturists are cloning a tree that barely exists anymore. The ice age gum tree, known to botanists as the Mongarlowe mallee, survives in the wild as just six individual plants on private land south of the Australian capital. The cloned trees now growing at the Australian National Botanic Gardens are meant to serve as an insurance population, a backup in case anything happens to the wild originals, according to ABC News.

The tree is little known outside botanical circles, and that obscurity is part of the problem. The ice age gum tree grows in low heathland on sloping ground in the New South Wales Southern Tablelands, near the small settlements of Mongarlowe and Windellama. Its leaves are small and curl backwards at the tip, the feature that gave the tree its scientific name, Eucalyptus recurva, and the reason a senior conservation horticulturist first thought it could not be a eucalypt at all.

A survivor from a colder age

The story of the tree starts with a landholder near Braidwood who brought specimens to the Australian National Botanic Gardens in August 1985. Botanist Michael Crisp formally described the species three years later. Peter Bredell, a senior conservation horticulturist at the gardens, told ABC News that his first reaction on seeing the plant was that it did not look like a eucalypt. He added that the wild plants are probably the last of an ancient remnant species that was around back in the ice age.

The age estimate comes from the largest ice age gum tree specimen. Growth of its woody lignotuber, the swollen base from which a mallee resprouts after fire, suggests the plant is somewhere between three thousand and six thousand years old. That would make it older than most human monuments, a single organism that has persisted through millennia of changing climate while its relatives vanished.

The ice age gum tree's wild population is spread thin. Three of the four known sites hold a single plant each, while the fourth holds a trio, and the Windellama site sits roughly thirty kilometres from the others. Genetic analysis by CSIRO has confirmed that each clump is a distinct individual rather than a shoot of one shared rootstock. No new wild plants have been found since the first discovery, and researchers consider it unlikely that many more remain undiscovered.

Why seeds alone cannot save it

For the ice age gum tree, a handful of individuals spread across kilometres is a reproductive dead end. The trees sit too far apart for reliable cross pollination, and the small amount of seed they do produce tends to be hybridised with other eucalypt species, which blocks viable pure seed. Natural regeneration is not known to occur, and seedlings raised in the past often lacked vigour and died young. Hand cross pollination carried out in 2002 and 2003 produced seed, but that seed is no longer viable.

Visits from plant enthusiasts add another pressure. According to the New South Wales threatened species profile lists trampling, collection of foliage samples, soil compaction and damage by vehicles among the threats to the wild plants, and a clay extraction site near the Windellama site raises the risk of hydrological change. Landholders now work with the state threatened species program, which has put up fences and signs to keep unauthorised visitors away from the trees.

Cloning as a backup plan

That is where cloning the ice age gum tree comes in. Staff at the Australian National Botanic Gardens are propagating the species, and the Australian Botanic Garden Mount Annan has researched grafting techniques for it as well. The goal is a living collection of genetically identical copies that can be kept safe, studied and eventually used to establish new populations. Genevieve Wright, a senior threatened species officer with the state threatened species program, described the cloned trees as an insurance population. She warned that if anything happens to the wild plants, the species faces extinction.

The approach has limits. Clones preserve the genetics of the existing plants but cannot add the diversity a healthy wild population would carry, so the work sits alongside protection of the originals rather than replacing it. Still, for the ice age gum tree, with no viable seed and no recorded natural recruits, a glasshouse full of copies is the most practical safeguard available. The cloned trees are already growing, and conservationists hope they will one day anchor a new population in the wild.