Catchment and reach-scale properties as indicators of macroinvertebrate species traits

1. We used catchment and reach-scale physical properties to predict the occurrence of specific species life history and behaviour traits of aquatic insects across fifty-eight catchments in a mixed land use basin. Catchment-scale attributes were derived using a geographical information system (GIS). Logistic regression techniques were used to model the relationships. 2. The reach-scale properties were highly predictive of species traits. Fourteen of the fifteen traits had significant models 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 attributes were best related to reach-scale physical features. This suggests that species traits exhibit strong relationships to local environmental conditions. 4. Catchment-scale variables had fewer significant models with species traits (four of fifteen), however these variables may have direct or indirect influence on reach-scale properties. 5. Catchment features, in particular surficial geology, influence macroinvertebrate assemblages through their control over channel morphology and hydrologic patterns. 6. The effects of land use were masked by geology (i.e. lacustrine clay geology and rowcrop agriculture were correlated), lack of detail in land use data and the aggregation of the species data. 7. These models reflect the coupling of local environmental conditions and the set of adaptations among the local taxa. These observations underscore the idea that habitat plays a major role in organizing stream assemblages. 8. Using these approaches, predictions can be made about 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 traits can improve the selection and evaluation of such indicators.