The stability-diversity relationship in stream macroinvertebrates: influences of sampling effects and habitat complexity

P>1. Theory predicts that the stability of a community should increase with diversity. However, despite increasing interest in the topic, most studies have focused on aggregate community properties (e.g. biomass, productivity) in small-scale experiments, while studies using observational field data on realistic scales to examine the relationship between diversity and compositional stability are surprisingly rare. 2. We examined the diversity-stability relationship of stream invertebrate communities based on a 4-year data set from boreal headwater streams, using among-year similarity in community composition (Bray-Curtis coefficient) as our measure of compositional stability. We related stability to species richness and key environmental factors that may affect the diversity-stability relationship (stream size, habitat complexity, productivity and flow variability) using simple and partial regressions. 3. In simple regressions, compositional stability was positively related to species richness, stream size, productivity and habitat complexity, but only species richness and habitat complexity were significantly related to stability in partial regressions. There was, however, a strong relationship between species richness and abundance. When abundance was controlled for through re-sampling, stability was unrelated to species richness, indicating that sampling effects were the predominant mechanism producing the positive stability-diversity relationship. By contrast, the relationship between stability and habitat complexity (macrophyte cover) became even stronger when the influence of community abundance was controlled for. Habitat complexity is thus a key factor enhancing community stability in headwater streams.