Authors:C. Ricotta, E. De Zuliani, A. Pacini, and et al.
Several evenness measures have been proposed for quantifying the distribution of abundance among community species, but none seems to be generally preferred. Since these measures have the common objective of summarizing community structure, they may be expected to be intercorrelated. In this paper, seven standard measures of evenness were calculated for 65 sample plots of ruderal vegetation within the archaeological sites of Paestum and Venosa (southern Italy). Principal component analysis was used to identify the primary aspects of community structure being characterized by these seven indices. The first two principal components explained 96% of total variance. A comparison of the first two principal components with the analyzed measures of evenness provides insight into what aspects of community structure they are expressing. While the first principal component is most sensitive to the relative abundances of rare species, the second principal component is clearly associated to changes in the abundance of the dominant community species.