Ordination methods and chironomid species in stony bottom streams

Abstract

Stony bottom streams in Italy were sampled in 369 sites in different years, and 174 chironomid species (or species groups) were identified. The species by sites matrix was submitted to different ordination methods, with the aim of outlining the major factors that are responsible of the observed species composition. The methods considered were principal component analysis (PCA), detrended correspondence analysis (DCA) and non-metric multidimensional scaling (MDSCAL). These methods assume different models describing the species-responses to the environmental gradients.