SPECIES TRAITS IN RELATION TO TEMPORAL AND SPATIAL HETEROGENEITY IN STREAMS - A TEST OF HABITAT TEMPLET THEORY

1. The habitat templet approach depends on defining templet axes appro priate to the organism(s) of interest, predicting the traits of specie s associated with different parts of the templet, and testing these pr edictions in a range of habitats whose positions in the templet have b een determined. 2. In this study of thirty-five benthic insect taxa at fifty-four tributary sites of the Taieri River on the South Island of New Zealand, we chose as the temporal axis the intensity/frequency of disturbance, defined in terms of bed movement during high discharge e vents. As the spatial axis, we postulated that three features would pr ovide refugia and therefore ameliorate disturbance-percentage of the b ed with low shear stress, percentage of the bed made up of large subst ratum particles and availability of interstitial space in the bed-from which we derived a combined multivariate refugium axis. 3. More distu rbed communities contained a significantly higher percentage of indivi duals possessing the following traits: small size, high adult mobility , habitat generalist (each predicted to confer resilience in response to disturbance), clinger, streamlined/flattened and with two or more l ife stages outside the stream (each predicted to confer resistance in the face of disturbance). When analyses were performed on the percenta ge of taxa having particular traits, the predicted positive relationsh ips with average bed movement were found for high adult mobility and h abitat generalist traits. 4. The percentage of variance in trait score s explained by intensity of disturbance was generally higher in sites with less refugia available and lower in sites further from the headwa ters. The percentage of variance explained was higher in sites recentl y subject to a major high discharge disturbance, suggesting that distu rbances tend to strengthen the pattern of preponderance of resilience/ resistance traits. 5. We mapped insect taxa onto the two-dimensional t emplet, following Grime et al.'s triangular terrestrial plant classifi cation. The full variety of resistance and resilience traits were repr esented in insect species throughout the templet, but taxa associated with more disturbed conditions generally displayed a larger number of resilience and resistance traits, combined, than taxa associated with more stable stream beds.