If a species ignored food in a particular category, then that was left unaffected, but among those categories where food was eaten, preferences were reassigned at random.These null models were then compared with the real data in terms of their pat- terns of resource use overlap. If competition is a significant force in determining community structure, then resource use overlap in the real communities should be less – and statistically significantly less—than that in the null models.
The results (Figure 6.21) were that in all communities, and for all four null models, the model mean overlap was higher than that observed for the real community, and that in almost all cases this was statistically significant. For these lizard communities, therefore, the observed low overlaps in resource use suggest that niches are more segregated than would be expected by chance alone, and that interspecific competition plays an important role in community structure.