The last ten years have seen an enormous increase in the development and application of multivariate methods in ecology; indeed the perceived importance of these methods for elucidating the complex interactions observed in community studies is shown by the number of recent books devoted to introducing the more common multivariate techniques to ecologists (Williams, 1976; Orloci, 1978; Whittaker, 1978a, b; Gauch, 1982; Legendre and Legendre, 1983; Pielou, 1984) and by the chapters added to new editions of more general texts on quantitative ecology (e.g. Greig-Smith, 1983; Kershaw and Looney,...