Species Abundance Plot

This menu can used to produce rank/abundance, ABC or k-dominance plots. A rank/abundance plot (or Whittaker plot) can be used to visualize species abundance distributions. In this plot, the number of individuals of each species are sorted in descending order, and the proportion of the total number of individuals for each species is then plotted on the log scale against the species rank. The shape of the rank/abundance plot can provide an indication of dominance or evenness, for example, steep plots signify assemblages with high dominance and shallower slopes indicate higher evenness.

A k-dominance plot displays the cumulative proportion abundance against the log species rank. For this type of plot, more elevated curves represent less diverse assemblages.

An abundance/biomass comparison (or ABC curve) is an adaption of the k-dominance curve where two measures of abundance are plotted: the number of individuals and biomass data. This plot is useful to explore the level of disturbance affecting assemblage.

Data format

Specifies to format of the data for the plot. For the rank/abundance and k-dominance plots the data can be supplied in different ways. Select Single variate to supply the individuals in a single variate. Alternatively, select Multiple variates, if the data are to be supplied in multiple samples of individuals.

Individuals

A variate containing the numbers of individuals per species.

Species

For a rank/abundance or k-dominance plot this can be used to specify a variate containing the number of species for the associated number of individuals in the corresponding element of Individuals. This field can be left empty if each of the values in Individuals corresponds to one species.

Biomass

For an ABC curve this species a variate containing the biomass data for each species.

Groups

A factor specifying the groups for different samples.

Samples

For multiple samples this allows you to specify one or more variates containing the individuals for different samples. Multiple selections can be transferred from the Available data list by clicking the

button.

Type of plot

Controls the type of plot that is to be produced. You can select either a Rank/Abundance Plot, k-dominance or ABC curve.

Display Summary

When selected, displays a summary of the number of individuals and species. If an ABC curve has been selected then the summary includes the W statistic.

Available Data

This lists data structures appropriate to the current input field. The contents will change as you move from one field to the next. Double-click on a name to copy it to the current input field; alternatively, you can type the name directly into the input field.