Cr. Townsend et al., SPECIES TRAITS IN RELATION TO TEMPORAL AND SPATIAL HETEROGENEITY IN STREAMS - A TEST OF HABITAT TEMPLET THEORY, Freshwater Biology, 37(2), 1997, pp. 367-387
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.