After the chytrid fungus was first discovered in Japan, studies have revealed the following facts,
1)Chytrid fungus is present naturely in Japan.
2)Japanese native amphibians are resistant to chytrid fungus.
3)Wild chytrid fungus in Japan has many haplotypes. In other words, this organism has surprising diversity in Japan. The chytrid fungus that originates from the Giant salamander shows a unique genetic cluster of haplotypes.
On the basis of these facts, we propose a new hypothesis, i.e., “Chytrid fungus has coevolved with native amphibians as a natural host in East Asia, including Japan.”. In other words, in the long process of the evolution of chytrid fungus and amphibians in East Asia, an equilibrium has formed between the hosts (amphibians) and the pathogen (chytrid fungus) which has continued up to the present. This hypothesis may explain the present state of chytrid fungus in Japan.
To prove this hypothesis, it is necessary to survey and analyze the genetic and ecological characteristics of chytrid fungus around the world, and research in East Asia is a priority.
