Bufo sachalinensis. Image credit: Othman et al. (CC BY 4.0)
The east Asian Asiatic toad (also known by the latin name Bufo gargarizans) lives in a wide range of habitats across East Asia including forests, meadows and cultivated land. However, it remains unclear how these toads evolved and became so widespread – partly because it has proved difficult for researchers to clearly define the species and what distinguishes it from other closely-related species of toads (collectively known as Bufo toads).
Othman et al. combined several bioinformatics techniques to study Asiatic toads and 38 other species of bufonid toads from across the globe. This approach found that Bufo toads first emerged in eastern Asia between 14 and 10 million years ago. This coincides with a point in time when large swathes of land in central Asia turned from adequate to sustain toad populations into desert, suggesting the change in climate prompted the toads to migrate eastwards from central Asia. The Bufo toads then divided into two groups of species: one in mainland East Asia and the other in Japan.
Furthermore, the study revealed there is more genetic diversity – that is, more variety in the DNA of individuals – in Asiatic toads than previously thought. The findings also help to define several other species of Bufo toads more clearly and describe a new toad species restricted to the Korean Peninsula, northeastern China and the Russian Primorye region: the Sakhalin toad (Bufo sachalinensis).
This work demonstrates that a large-scale study of many species across the globe can be used to understand how the species evolved and more clearly distinguish one species from another. The findings of Othman et al. will be of interest to both professional and citizen scientists interested in the natural history of Asia. Furthermore, as several species of Bufo toads are in decline in the wild, they provide evidence that may aid future efforts to conserve them.
