Some tests for niche limitation by examination of species diversity in the Dunedin area, New Zealand

Fifteen plant communities were sampled, each by five randomly‐placed quadrats. Bryophyte and vascular plant species were recorded. There were considerable differences between communities in species diversity. These agree with some theories, and conflict with others. Types of community that are young, in evolutionary time, did not seem deficient in species. Human disturbance, and the consequent invasion of exotic species, had very little effect on species diversity, but this seemed to be because of a balance between opposing trends, difficult to relate to niche limitation. Correlation gave no evidence that exotic species displaced natives from a fixed number of niches. Within‐community variance in species richness is significantly greater than that predicted from a null model, providing no evidence for the niche limitation theory.