PATTERNS OF ORDINATION AND CLASSIFICATION INSTABILITY RESULTING FROM CHANGES IN INPUT DATA ORDER

Random rearrangement of entry order in three data sets often changed o rdination and classification results based on Reciprocal Averaging. Re sults varied with the data set and method used. Eliminating infrequent ly occurring species largely reduced, but did not always eliminate, th e variability. Overall, results appeared related to data set complexit y, the type of data or transformation, and the analysis method used. D etrended Correspondence Analysis had the greatest variability of the o rdination methods tested. Results from quantitative data were usually more variable than presence/absence data. Variation in cluster analysi s was related to the number of tie values in the similarity matrix. De tailed tests using randomization of entry order of individual data set s with each of the programs to be used are needed to individually asse ss the effects on the results.