This amazing story reports the longest ever recorded dispersal event. Using genetic evidence biogeographers have proved that two populations of Acacia tree in Reunion Island (Indian Ocean) and Hawaii represent a single species. The Reunion Island population became established around 1.4 million years ago when a seed from Hawaii was transported 18,000 kilometres, probably attached or inside a bird.
The article also details some other long-distance dispersal events, but none quite as extraordinary as this one. However, these dispersal events are changing how biogeographers understanding of species distributions, with an increasing recognition of the role of chance - single rare events which have long-term and profound implications for species distributions and patterns of biodiversity.
The event is remarkable not just for the sheer distance covered — some 18,000 kilometres, almost the farthest apart that any two points on land can be — but that it occurred between two small islands. Koa seeds are unlikely to have floated to Réunion — they will not germinate after being soaked in seawater, and the trees grow in the mountains, not near the shore. The researchers propose that a sea bird brought a seed from Hawaii to Réunion in its stomach or stuck to its feet in a one-off event some 1.4 million years ago