Ikegami Takashi, Kaneko Kunihiko
The Graduate School of Science and Technology, Kobe University, Rokkodai, Nada-ku, Kobe 657, JapanDepartment of Pure and Applied Sciences, College of Arts and Sciences, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153, Japan.
Chaos. 1992 Jul;2(3):397-407. doi: 10.1063/1.165882.
Host-parasitoid systems with evolving mutation rates are studied. By increasing the growth rate of hosts, the diversity of both species is maintained dynamically. For the lower growth rate, diversity is brought about by mere parasitism. The average mutation rate for parasites is elevated to a high value, while that for hosts is suppressed at a low level. For the higher growth rate, the mutation rates for both hosts and parasites are elevated to form a symbiotic cluster connected by on-going mutation. This symbiotic state is sustained through a chaotic oscillation keeping some coherency among species. For a flat landscape for hosts, dynamical clustering of oscillation is observed. Lyapunov spectra of such oscillations show that high dimensional chaos with small positive exponents underlies in the symbiotic state. This weak high dimensional chaos, termed "homeochaos," is essential to the maintenance of symbiosis in ecosystems.
对具有不断演变的突变率的宿主-寄生蜂系统进行了研究。通过提高宿主的生长速率，两个物种的多样性得以动态维持。对于较低的生长速率，多样性仅由寄生作用产生。寄生虫的平均突变率升高到较高值，而宿主的平均突变率则被抑制在较低水平。对于较高的生长速率，宿主和寄生虫的突变率都升高，形成一个通过持续突变相连的共生簇。这种共生状态通过在物种间保持一定连贯性的混沌振荡得以维持。对于宿主的平坦适应度景观，观察到振荡的动态聚类。此类振荡的李雅普诺夫谱表明，共生状态下存在具有小正指数的高维混沌。这种微弱的高维混沌，称为“同态混沌”，对于生态系统中共生关系的维持至关重要。
