Original paper

Linking scale and diversity partitioning in comparing species diversity of caddisflies in riffle and pool habitats

Schmera, Dénes; Erős, Tibor

Abstract

Assessing and interpreting biodiversity is a key issue of current ecology and sampling is the first and most critical step in biodiversity assessment. We focused on how sampling scale influences the mesohabitat level species diversity components (i.e. alpha, beta, gamma) of caddisflies in a natural submontain stream. We interpreted scale as the relationship between observation unit size (grain), sample size (number of replicates) and total sampled area (sampling effort), and examined in three simulated experiments, how the individual and joint effects of these scale components influence the difference of caddisfly diversity between riffle and pool habitats. Additive partitioning of diversity into within observation unit (α), among observation unit (β) and total diversity components (γ) in a scale-dependent manner showed that scale had a fundamental role in (1) quantifying values of diversity components and (2) in detecting differences between assemblages. Although sites showed considerable variability, the study clearly demonstrated that sample size and total sampled area are the most important and critical scale components of sampling, while the size of the observation unit might be indifferent. The analytical method applied here can be used for any aquatic assemblage collected with a sampling device of well defined area (or volume) and at any levels of the habitat hierarchy. The study reveals the importance of the among observation unit component (i.e. small scale beta diversity) in shaping total diversity and calls attention to the careful consideration of scale in environmental assessment and monitoring.

Keywords

diversity partitioningsamplingscalespecies diversityspecies-area relationshiptrichopterastream bioassessment