Rolecek et al. (2010) proposed a modified formula for calculation of similarity between pair of communities (samples, plots, releves). We derived it from the Sorensen-Dice's coefficient to be consistent with the concept of similarity frequently used in ecology. The ecological similarity index (ES index) is based on presences (not abundances) of species in compared communities and it exploits information on all species, not only the shared species.
Here, you can download an Excel file with macro calculating this modified index of similarity.
Let us know how it works with your data. Thank you!
Contact:
Jan Rolecek honza.rolecek (at) centrum.cz
Katerina Kintrova kintrova (at) sci.muni.cz