Choix des métriques qualitatives en analyse d'inertie. Implications en écologie marine benthique

The choice of a distance is the starting point of any multivariate analysis. The purpose of this work is to provide a clearer ecological understanding of the various similarity indices based on the presence-absence criterion. The so-called qualitative indices are obviously divided into two kinds depending on whether negative matches (double absences) are included or not. The concept of pre-order between distances provides a possibility of grouping the coefficients satisfying the same inequality relationships: a basic scheme of classification is proposed according to these two criteria. Theoretical considerations followed by practical applications to benthic data from the North Bay of Biscay Shelf reveal the ecological significance of the different qualitative indices. Principal co-ordinate analysis is used to illustrate differences between structures defined by various distances. A special section is devoted to the problem of dual species samples in principal co-ordinate analysis.

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Contribution n° 405 du Département Scientifique du Centre Océanologique de Bretagne.