The spidery wattle (Acacia araneosa) is a national treasure.

This plant is named for its spidery, leaf-like phyllodes and shares the same iconic golden flowers as Australia’s floral emblem, the golden wattle (Acacia pycnantha).

The spidery wattle is extremely rare, found only in a tiny area of South Australia’s Arkaroola Wilderness Sanctuary and Vulkathunha-Gammon Ranges National Park. This, alongside its unusual appearance, makes it a distinctive and beloved part of the landscape.

But this local icon is under threat. In the late 1830s, the first pastoral leases – which allowed livestock grazing on government land – were granted in South Australia. This significantly reshaped the state’s landscapes and ecosystems.

Our new study shows since that period, the spidery wattle population has drastically shrunk by about 98%. If this trend continues, the future of this unique species looks grim.

Thankfully, we can do something about it.

The spidery wattle has long puzzled scientists.

For years, researchers studying this unassuming plant noticed seed from the spidery wattle would sometimes “revert” to the form of another common wattle species, the silver wattle (Acacia rivalis). The silver wattle is a more widespread species than the spidery wattle, but grows in the same area.

This phenomenon could be explained by phenotypic plasticity — the ability of an organism to modify its physical traits or behaviour........

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