CATCHMENT AND REACH-SCALE PROPERTIES AS INDICATORS OF MACROINVERTEBRATE SPECIES TRAITS

1. We used catchment and reach-scale physical properties to predict th e occurrence of specific species life history and behaviour traits of aquatic insects across fifty-eight catchments in a mixed land use basi n. Catchment-scale attributes were derived using a geographical inform ation system (GIS). Logistic regression techniques were used to model the relationships. 2. The reach-scale properties were highly predictiv e of species traits. Fourteen of the fifteen traits had significant mo dels with concordance values greater than 68%. Cross-sectional area at bank full discharge, % shallow, slow-water habitats, and % fines were the most important variables. 3. Life history and behavioural attribu tes were best related to reach-scale physical features. This suggests that species traits exhibit strong relationships to local environmenta l conditions. 4. Catchment-scale variables had fewer significant model s with species traits (four of fifteen), however these variables may h ave direct or indirect influence on reach-scale properties. 5. Catchme nt features, in particular surficial geology, influence macroinvertebr ate assemblages through their control over channel morphology and hydr ologic patterns. 6. The effects of land use were masked by geology (i. e. lacustrine clay geology and rowcrop agriculture were correlated), l ack of detail in land use data and the aggregation of the species data . 7. These models reflect the coupling of local environmental conditio ns and the set of adaptations among the local taxa. These observations underscore the idea that habitat plays a major role in organizing str eam assemblages. 8. Using these approaches, predictions can be made ab out the ability of various taxonomic groupings to track environmental change through time, or for projecting the impact of alternative land management scenarios. Identifying fundamental life history and other t raits can improve the selection and evaluation of such indicators.