An Algebraic Derivation of Chao’s Estimator of the Number of Species in a Community Highlights the Condition Allowing Chao to Deliver Centered Estimates

Figure 1

Typical shape of the “SAD” when the number of unrecorded species is decreasing as a negative exponential of the sample size. The sum of abundances is normalised at 100% (open circles: total species richness = 20; black diamonds: total species richness = 50).