The application of ecological theory to palaeoecological studies, with special reference to equilibrium theory and the Ordovician System

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Abstract
In light of recent applications of equilibrium theory to paleoecological investigation, the origins and scope of the model are reviewed as a perspective for considering the viability of such applications in the analysis of Ordovician faunal associations. Alternative methods for the detection of immigration and emigration patterns are advanced in favor of other recently proposed techniques. The mid-Caradoc Gelli-grin Formation is used as an example of a well sampled fossiliferous deposit from which comprehensive faunal data can be derived for use in the detection of intra-association fluctuations in faunal composition. Different methods of defining such fluctuations produce consistent results. Saturation, area effect and overshoot effect are aspects of equilibrium theory with potential for application in the paleoecological field. The calculation of the coefficient of variation for 8 faunal associations discussed here is a useful method for determination of the degree of saturation of such associations; comparable associations show similar saturation values. The faunal associations included Onniella-Sericoidea, Howellites-Kloucekia, Nicolella-Onniella, Howellites-Paracraniops, Bicuspina set, Lingulella set, Pseudolingula set and a Nuculites-Cryptolithus dominated association.