Produces rank/abundance, ABC and k-dominance plots (D.A. Murray).
|Controls printed output (
||Controls the type of plot (
||Defines the groups if there is more than one sample|
||Number of individuals per species|
||Number of species|
||Biomass data for each species for an ABC plot|
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.
The numbers of individuals per species are specified using the
INDIVIDUALS parameter. The
SPECIES parameter specifies a variate containing the number of species for the associated number of individuals specified in the corresponding element of
SPECIES can be omitted if each of the values in
INDIVIDUALS corresponds to one species. The
GROUPS option can be used to plot the relative abundance for different samples.
PLOT option can be used to produce a rank/abundance plot, k-dominance curve and an ABC curve. You can display a summary of the number of individuals and species by setting the option
PRINT=summary. Selecting this option will also display the W statistic for an ABC curve.
For a rank/abundance plot the numbers 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. In a k-dominance plot the cumulative proportion abundance, or for an ABC curve the cumulative percentage abundance, is plotted against the log species rank.
The W statistic for an ABC curve is defined by
W = ∑i (Bi – Ai) / (50 × (S – 1))
where S is the total number of Species, Bi is the biomass value of each species rank i, and Ai is the abundance value of each species rank i.
If a parameter is restricted the graphs will be drawn using only those units included in the restriction.
Magurran, A.E. (2003). Measuring Biological Diversity. Blackwell, Oxford.
Commands for Ecological data.
CAPTION 'ECABUNDANCEPLOT example',!t(\ 'Data are number of dung beetles species found on dung pats',\ 'around Bangalore in the Western Ghats, India (see Magurran',\ 'Worked example 4, pages 226-229.'); STYLE=meta,plain VARIATE [VALUES=897,339,144,98,70,63,62,25,16,7,7,6,5,2,2,2] Individuals ECABUNDANCEPLOT Individuals