Plecoptera and Ephemeroptera species assemblages in the Usk river system, Wales
Millett, M. C.; Learner, M. A.
Archiv für Hydrobiologie Volume 143 Number 3 (1998), p. 307 - 334
published: Nov 4, 1998
ArtNo. ESP141014303007, Price: 29.00 €
The distribution and abundance of Plecoptera and Ephemeroptera species in the Usk river system, South Wales, were studied in relation to the physico-chemical environment. Faunal samples were collected from riffles during summer 1989 at 47 sites distributed throughout the river system. Twenty-four species were collected; 10 Plecoptera and 14 Ephemeroptera. The sites were classified by two-way indicator species analysis (TWINSPAN) on the basis of faunal similarity, and the "cohesiveness" of the resulting site groups was examined using detrended correspondence analysis. Relationships between eight site groups identified using TWINSPAN and various environmental variables were explored using product-moment correlation analysis and multiple discriminant analysis (MDA). Membership of the TWINSPAN site groups could be determined with little error using sub-sets of environmental variables; using MDA 72 % of the sites were assigned correctly to their TWINSPAN Level 3 groups on the basis of six variables. This implies that on a catchment/sub-catchment scale the structuring of the Plecopteral/Ephemeroptera fauna in the Usk system is driven largely by the abiotic environment. TWINSPAN was also used to classify the fauna into species associations. Six associations were defined which were characteristic of different regions of the main river and its tributaries.