It is difficult to find evidence that naturally low diversity communities are more susceptible to invasion than naturally high diversity communities. The tropical biota is so diverse and complex that large fluctuations might go largely unnoticed. Tilman and Downing 12 suggest that primary productivity in more diverse plant communities is more resistant to, and recovers more fully from, a major drought. 207 plots of prairie grasslands differing in species richness from 1 to 26. Measured resistance as relative rate of community biomass change from 1986, the year before a drought, to 1988, the peak of the drought.
Small values indicate high resistance.
Drought resistance is an increasing function of community diversity. Saturates at about 10-15 species.