How Indigenous people shaped Australia ’s curious geography of plants

On shady, densely wooded riverbanks in eastern Australia, the black bean tree is easily missed. It can reach 12 stories tall, but Castanospermum australe mostly blends in with its rainforest peers. Each November, however, it catches the eye as sprays of large red and orange blossoms adorn its dark, glossy leaves. Six months later, cylindrical pods longer than a banana encase three to five large seeds. The seed pods are buoyant, so those that end up in the water can drift away, allowing the seeds to germinate far from the parent tree. But each seed weighs about as much as a mouse—too heavy to be carried off by the wind or easily dispersed by birds and most rodents. Therein lies a mystery: Black bean trees sprout not just along waterways and coastal areas, but also along ridges high above rivers, far from the water. A few years ago, Maurizio Rossetto, an evolutionary ecologist at the Royal Botanic Garden Sydney, began to wonder how they got there. One potential answer was that these unusual patches were the remnants of forests created long ago by large, now extinct animals that once helped spread black bean seeds across eastern Australia. Rossetto knew that most large-seeded plants thought to have lost their ancient distributors had retreated to small areas, yet the black bean trees are widespread. So, he wondered about another possible disperser: prehistoric Australians, who arrived on the continent at least 50,000 years ago. Rossetto was ex...
Source: ScienceNOW - Category: Science Source Type: news