Diversity ordering
|
|
Top Previous Next |
|
Two diversity ordering methods, Rényi and Right-tailed Sum, are listed when the diversity ordering button is selected. Simply click on the icon to run either method.
Different diversity indices may differ in the ranking they give to communities (Hurlbert, 1971; Tothmeresz, 1995). An example from Tothmeresz (1995) illustrates the point. Consider three artificial communities with the following sets of species abundances for each of which diversity has been calculated using both Shannon-Wiener (H) and (2) Simpson's (D): Community A : {33,29,28,5,5}, H = 1.3808, D = 0.7309, Community B: {42,30,10,8,5,5}, H = 1.4574, D = 0.7194, Community C: {32,21,16,12,9,6,4}, H = 0.639, D = 1.822,
Because H(B) > H(A) it could be argued B is the most diverse, however, as D(A) > D(B) the opposite conclusion could also be entertained. Communities such as A and B which cannot be ordered are termed non-comparable.
Such inconsistencies are an inevitable result of summarising both relative abundance and species number using a single number (Patil & Taillie 1979). Diversity profiles offer a solution to this problem by identifying those communities that are consistent in their relative diversity. This requires the use of a diversity index family, of which there are a number to choose from (Tothmeresz, 1995).
The output window The output is a tabbed display. The first tab shows the graph of the indices for each sample. The graph can be changed, copied or saved using the Chart menu on the main window. The second tab shows a table of the plotted data. These data can be printed using File: Print, or the Print button on the Chart toolbar, and copied using the Edit menu. Diversity ordering results in a line for every sample, which for a large data set can result in a meaningless mess if they are all plotted together. The program selects only the first 16 samples to plot. To select the samples to be displayed on the graph use the Select Data tab.
|
