Use this biodiversity measure when counts or incidences were collected with comparable sampling effort and the estimator matches the study design. It can summarize richness, dominance, evenness, or compositional difference.

Observed species

An integer count greater than or equal to 1, expressed in species.

Sample count

An integer count greater than or equal to 2, expressed in samples.

Uniques

An integer count greater than or equal to 0, expressed in species.

Doubletons

An integer count greater than or equal to 0, expressed in species.

The implementation follows this calculation rule: Estimate total species richness from incidence data across samples using the Chao2 estimator.

Chao2 estimate

The calculated chao2 estimate in species.

Different diversity indices weight rare and common taxa differently. Detection probability, sample coverage, taxonomic resolution, zero counts, and unequal effort can dominate comparisons; proxy estimators are not interchangeable with their full published forms. The output is explicitly an estimate or proxy; preserve that label when reporting it.

Report observed richness, abundance or incidence data, and sampling effort beside the index. Coverage-based rarefaction, accumulation curves, and more than one Hill-number order provide a fuller view of community structure.

• First Order Jackknife

  Estimate species richness with the first order jackknife from unique species across incidence samples.

• Bootstrap Richness Proxy

  Compute the limited richness proxy Sobs + singletons divided by sample count. A full bootstrap richness estimator requires each species' observed incidence frequency.

• Chao1 Estimator

  Estimate total species richness from singletons and doubletons in a single sample using the Chao1 estimator.