Assessing the temporal and spatial components of littoral macroinvertebrate diversity variation

We used a hierarchical sampling design to assess the relative importance of temporal and spatial variation to lake littoral macroinvertebrate species diversity. We collected replicate samples (n=10) from nine littorals, nested within three lakes, during three consecutive years. Additive partitioning was used to determine the most relevant spatial and temporal scales for diversity monitoring in lake littorals. We assessed hierarchical variation of diversity for three metrics: species richness and two diversity indices. The inter-annual variation of species richness (20%) was significantly higher than expected by chance, whereas inter-annual variation in Simpson's and Shannon's diversity indices was negligible (0.6-2.3 %). The largest proportion of diversity variation was always associated with the sample scale (α₁ + β₁; 45 to 94% of total variation). Our results indicate that the level of annual diversity variation does not seriously impair our ability to obtain reliable estimates of lake littoral macroinvertebrate diversity. We suggest that sampling effort in littoral diversity monitoring should be allocated primarily to adequate replication at multiple spatial scales.