Discovering the Origins of Amami Oshima through Wild Ginger

Wild gingers are currently in full bloom in Amami Oshima. During a nature tour in the forests of Tatsugo Town, I found the blossoms of the broad-leaf wild ginger.

Spotted Broad-leaf Wild Ginger in Tatsugo Town. The visible flower at the base.

Wild ginger is a unique plant. It takes 100 years to expand its habitat by just one meter. This slow expansion is due to its reliance on ants for seed dispersal. Ants carry the seeds to their nests, seeking the sugars, amino acids, and fatty acids attached to the seeds. As the transported seeds germinate in the process, wild ginger spreads its habitat.

The view of the Tatsugo bay

By the way, do you know how Amami Oshima was formed? Long ago, it separated from the Eurasian continent. Wild ginger, though a tiny plant, serves as evidence of this separation. Similar species of wild ginger to those in Amami Oshima can be found on the continent. It is believed that these two species were once the same, evolving into different types after the island branched off. Since wild ginger relies on ants for seed dispersal, it couldn’t have spread through bird-mediated dispersal after the land was separated by the sea. In other words, during the era when Amami Oshima was connected to the continent, ants facilitated seed dispersal, and the island formed later.

This example illustrates observing small plants can reveal stories on a larger scale.