Species Accumulation Curves

This menu can be used to produce species accumulation and rarefaction curves. Species accumulation curves show the rate at which new species are found within a community and can be extrapolated to provide an estimate of species richness. The simplest type of species accumulation curve is the collectors curve. This plots the cumulative number of species recorded as a function of sampling effort (i.e. number of individuals collected or cumulative number of samples). The order in which samples are included in a species accumulation curve will influence the overall shape. A smooth accumulation curve can be produced by repeating a process of randomly adding the samples to the accumulation curve and then plotting the mean of these permutations. This menu can be used to produce these type of species accumulation curves and can plot a Coleman curve of the expected number of species.

Rarefaction is a method that can be used to estimate the number of species that would be found if sampling effort was reduced to a specified level. This then allows comparisons amongst communities where sampling effort is unequal. This menu can also be used to produce rarefaction curves. Rarefaction curves are viewed as moving from right to left, whereas species accumulation curves move from left to right.

Method

Specifies the method for the plot. For the collector and rarefaction curves you can select between individual- and sample-based methods.

Individual-based method

For individual-based methods the data can be supplied using the following options:

Individuals For a collector curve this specifies a factor or variate containing the individuals in the order that were collected. For rarefaction this specifies a variate containing the number of individuals for each species.

Groups For the collector method this specifies a grouping factor for samples.

Sample-based method

For sample-based methods the data can be supplied using the following options:

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 Collector, Random, Coleman curve or Rarefaction.

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.

Action Buttons

Run	Run the analysis.
Cancel	Close the menu without further changes.
Options	Opens a dialog where additional options and settings can be specified for the graph.
Defaults	Set the menu settings back to the default settings. Clicking the right mouse on this button produces a shortcut menu where you can choose to set the menu using the currently stored defaults or the GenStat default settings.
Store	Opens a dialog where you can store results from the analysis.

Individuals	For a collector curve this specifies a factor or variate containing the individuals in the order that were collected. For rarefaction this specifies a variate containing the number of individuals for each species.
Groups	For the collector method this specifies a grouping factor for samples.