Use of the Multi-Response Permutation Procedure and Indicator Species Value for the statistical classification of the gypsicolous Iberian scrub communities

摘要

The Iberian gypsophilous scrub communities, belonging to the phytosociological order Gypsophiletalia (Bellot 1952)Bellot & Rivas Goday 1957, are considered as priority ecosystems for conservation because of their richness in endemic and s tenoecious species. Six complete revisions and a number of partial revisions of Gypsophiletalia have been published up to now, producing over'100 phytosociological tables and about, 800 vegetation releves.This large amount of information has been analysed here to reevaluate this phytosociological order. The statistical techniques of Multi-Response Permutation Procedure (MRPP) and Indicator Species Value (IV) have been carried out on this data set and the results have been compared with data obtained from cluster analysis. Our results reveal the inconsistency and lack of objectivity of some of the previous syntaxonomical typologies. We conclude that objective classifications must be based, on clearly defined criteria easy to replicate in following the same procedures. Both IV and MRPP have proved useful techniques, not only for the clarification of the diagnostic potential.value of taxa, but also for the production of objective syntaxonomical typologies.