February 2006: Second (2.1) version. The second generation of the Species Richness module both adds and eliminates features compared to the first. The main addition is that the eco-tool now calculates an analytically-derived sample-based rarefaction curve for a set of community samples, as first presented by Colwell, Mao and Chang (2004). This technique improves upon previous methods of generating such curves, such as the randomization method implemented in the software package EstimateS prior to version 7.0 (current versions also use the analytical method). The improvements are several:
- The analytical method produces a smooth curve, representing the expected number of species to be found in a set of samples.
- The analytical method, being based on an underlying statistical model, allows the generation of more sensible confidence intervals.
- The analytical method is faster, as it does not rely on repeated randomizations of the original dataset.
The new version also calculates more variants of the Chao 1 and 2 estimators, using the decision rules outlined in the EstimateS manual to choose a version appropriate to the dataset under consideration. It also tweaks various other estimation procedures.
June 2004: First (1.1) version.
June 2004: Development version.