References

Ecological system is complex: a wide variety of interacting species consist each ecosystem. It is dynamically organized and maintained in evolutional time scale. It is a challenge to clarify the essence why ecoevolution could achieve such complex self-organization. The answer will be simple and uni-versal, because there are wide variety of ecosystems on the earth, and there should have been more variety in past. Such variety will not be realized without some simple universal mechanism. Models of ecoevolution dynamics are compared to reach the universal feature[1, 2], and it is found that a skew pro le in life-time distribution function of species is the one. After a study of the simplest model, in an Ising sense, a random walk in a number-of-species space with so-called the“Red-Queen Hypothesis”is proposed and the skew pro le turns out to be due to a stretched exponential function with exponent 1/2[3]. Such stretched exponential prole well-explains not only fossil data