Abstract
Although spatial scale plays a critical role in estimates of biodiversity, most empirical studies ignore scale or use only simple controls for sampling intensity. In a meta-analysis of studies that measured biodiversity responses to numerous ecological drivers across scales, we found nearly universal scale-dependence: effect sizes either greatly increased or decreased across scales, and nearly 10% switched directions across scales. Next, we show how accumulation and rarefaction curves can be used to dissect the effects of biodiversity scaling based on three components: total number of individuals (N), the shape of the species abundance distribution (SADs), and the pattern of spatial aggregation. In a second meta-analysis of studies with multiple rarefaction curves, ∼30% of them crossed, and the three components of biodiversity were uncorrelated, contradicting conventional wisdom that most biodiversity measures are strongly intercorrelated. These results imply that there is no single ‘magic metric’ or scale for measuring biodiversity, and that multiple measures and scales are necessary to quantify biodiversity patterns. We use a case study of nutrient additions in experimental ponds to illustrate how this multi-scale perspective reveals the responses of biodiversity to ecological drivers, and allows for a more informed search for possible mechanisms.
Statement of Authorship
JC and BM conceived the study and the overall approach, and all authors participated in multiple working group meetings to develop and refine the approach. JC collected the data for the meta-analysis that led to Figure 2 and S1; BM collected the data for the meta-analysis that led to Fig. 6,7; SB and FM did the meta-analyses; FM did the simulations for Fig. 5; DM, FM and XX wrote the code for the analysis used for the recipe and case study in Figure 8. JC, BM and NG wrote first drafts of most sections, and all authors contributed substantially to revisions.