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Changes in measures of niche breadth and overlap do not necessarily reflect changes in the intensity of competition. While niche measures, like all static indexes, are poor descriptions of dynamic processes, most niche measures have the additional problem of not being explicitly derived from specific models of competition. I show that the symmetric measure of niche overlap is equivalent to the cosine of the angle between the consumption vectors in Tilman's model of resource competition. Niche breadth is shown to be related to the orientation of the consumption vector. This provides an easy and clear way to visualize the relationship between niche measures and the equilibrium levels of consumption and resource availability in cases where the assumptions of Tilman's model are met.
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