Exceedingly cool results.
Somehow, wherever this small bat thrives, its presence also creates a niche for a bigger bat, which evolves from... the small bat. You get a string of islands with the simultaneous presence of the small bat and the big bat that re-evolves from it every time....
The phenomenon is so weird that people thought it was just 2 different species that colonized the islands in parallel. It's just one species with a recurring sub-branch.
