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, 1985). Two reasons can be
put forward to explain this development. The first is undoubtedly the
increasing availability of cheap computing power which makes it feasible
to analyse the large data matrices involved in community studies. The
second, perhaps less widely appreciated, is the change in emphasis of
theoretical work on multivariate analysis, away from the development of
formal statistical models and associated distribution theory towards
descrip- tive techniques for exploring pattern in data sets and
providing succinct summaries and displays. This new approach, termed
'pattern analysis' by Williams (1976), has led to a range of statistical
techniques which have been enthusiastically taken up by ecologists to
replace the collection of ad hoc procedures developed over the years for
analysing community data.