What factors determine the distribution of organisms?

 

This is one of the most fundamental and classic questions in biology, which has been studied in the field of biogeography. By deciphering the patterns of the distribution of organisms, we will be able to understand how the immigration that causes the geographical distribution occurs, the process of evolution and speciation, and the diversification process on Earth. 

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Biogeography used to be a discipline with a strong descriptive aspect, but the recent systematic macroevolutionary approaches have promoted "generalized biogeography." On the other hand, the uniqueness of each species' biogeographic history is being overlooked.

 

How has idiosyncrasy of historical biogeographical events of different species influenced the diversification processes?

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What's interesting about the Japanese birds?
 

Birds can fly. This allows them to move not only on land, but also over oceans and deserts that many other animals cannot cross.

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Japan is a land-bridge island. In the geological past, during the Ice Age, some parts of Japan were connected to the continent. Repeated ice ages over the course of several million years, turned Japan into a "continental peninsula''.

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Then, Japanese birds should provide an interesting insight. Many animals, including mammals, must have been forced to migrate to Japan in large numbers during this land-bridge period.

 

However, in birds, some did over-sea dispersal, while others arrived in Japan across land-bridges. Japan should be a "melting pot" of birds with many different biogeographic histories.

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If each species has a diverse biogeographic history, how has this diversity affected their evolutionary paths? Japanese birds provide a suitable system that can answer this question.