Ecological Equivalence: Niche Theory as a Testable Alternative to Neutral Theory - Recent Advances and Issues in Environmental Science - page 7

Figure 4. Simulated steady-states of species-area relationships (SARs). The SARs each show mean ±
s.e. of three replicate communities. See Materials and Methods for input parameter values and the
process of random species assembly.
The extended tail of rare species seen in the Figure 3 SADs is caused by single-in-
dividual invaders replacing random extinctions of n-individual species. Further trials
confi rm that reduced dispersal limitation exacerbates the negative skew from the log-
normal distribution, while sustaining a higher total density of individuals. The extinc-
tion-invasion imbalance sets the equilibrium species richness, S , as a power function