Evaluating Expectations Deduced from Explicit Hypotheses about Mechanisms of Competition

Publisher Website
Google Scholar
Abstract
Our primary purpose is to correct the fallacy that interspecific competition is proportional to realized niche overlap. Two independent but nonetheless complementary arguments are corroborated by actual and simulated instances in which overlap declines during exploitative and interference competition, both of which evidently can lead to nonoverlapping patterns of resource exploitation (i.e., partitioning), collectively constituting a third. The first argument, which is analytical, involves deducing species' expected per caput competitive effects from a mechanistic model and demonstrating that the probabilities that individuals of competing species exploit alternative resources, which comprise the portion of such expressions corresponding to niche overlap, are pre- rather than post-interactive. Our second argument, which is empirical, involves demonstrating how well the probabilities corresponding to realized (i.e., S th) and other partial niche overlaps estimate competition by comparing the per caput effects observed upon simulating this model with variously parameterized expectations. Although the suggestion that competition was reduced by species foregoing potential resources being exploited by others brought this fallacy to our attention, we have become convinced that it would have been exposed decades ago had multiple resource-consumer models been used as explicit hypotheses about mechanisms of competition. Hence, our secondary purpose is to advocate use of the otherwise conventional hypothetico-deductive paradigm.