Random matrices have been widely studied as neutral models for the stability of large systems. However, ecosystems frequently display both a hierarchical trophic organization and organization into a family of loosely coupled subsystems. It is shown that systems with these features have lower Lyapunov stability than corresponding random systems. Thus ecosystems organization arises from other biological and physical factors. Moreover, the simulation methods presented here can be readily used to determine the effect of system structure on neutral models for other similarly complex systems.
The Hellinger (arccos) distance is examined for the purpose of demonstrating to what extent it represents the differences among populations. When the Hellinger distance is employed to estimate gene frequencies, a result very similar to that of the maximum likelihood (Bernstein) method can be gained. It is pointed out that in palaeoserological examinations the Dobson/Ikin method usually mentioned as Fisher method is not equivalent to the Bernstein method.
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