Explaining Madagascar's extraordinary levels of plant and animal endemism has been called "one of the greatest unsolved mysteries of natural history." The long separation of Madagascar from Africa and India explains only some aspects of the island's endemism. Even more intriguing is that many of these plants and animals have very small distributions on the island, something that is called micro-endemism.
For the first time, this new research presents a comprehensive theory explaining how so many animals came to be limited to such small geographic areas across the island, which lies off the eastern coast of Africa. In some lowland areas of the island these animals tended to be isolated by the configuration of certain watersheds, and this isolation led to speciation, the evolution of new species.
Using an analysis of watersheds in the context of paleoclimatic shifts, the authors provide a new mechanistic model to explain the process of explosive speciation on the island. Existing data show that substantial climatic shifts took place during the end of the Tertiary, as well as more recently during the Quaternary. The latter period is also known as "The Age of Man."
When the climate was dry and cold, considerable portions of the Earth were covered by glaciers. On Madagascar, habitats at higher elevations would have remained more humid, as compared to the drying-out of more lowland areas. Therefore, groups of animals tended to "retreat" to higher elevations along riverine habitat that would have remained relatively humid during these periods of climatic change. The animals that did not "retreat
Contact: Greg Borzo