EFFECTS OF MICROSPATIAL COMPLEXITY ON A HERBIVORE EPILITHON INTERACTION IN AN AUSTRALIAN UPLAND STREAM

1. Increases in spatial heterogeneity may provide more food, create ne w resources or interfere with the foraging activities of a herbivore. 2. Three colonization experiments were performed in an upland stream t o investigate the effects of one type of spatial heterogeneity (groove s on the substratum) on the relationship between an abundant herbivore , Agapetus monticolus (Banks, Trichoptera), and the epilithon on which it feeds. 3. The results indicate that grooves do not provide any dif ferent resources or interfere with the foraging activities of A. monti colus, but may increase food abundance, although the effect of grooves on food abundance appears to vary temporally. 4. Temporal variation i n the effects of microspatial complexity raises the possibility that i ts importance to the community may be over- or underestimated unless e xperiments are designed to incorporate this temporal variation.