Figure 1.

Illustration of the relationship between observed β-diversity and spatial scale (grain size) showing a bi-phasic curve: (1) large variation at small spatial scales, and (2) small variation at large spatial scales. Decreasing γ-diversity with increasing latitude is well known [3], and if β-diversity is correlated with γ-diversity at small spatial scales, we should also expect β-diversity to decline with increasing latitude. However, reliance of β-diversity on γ-diversity is mathematically invalid as long as α-diversity is large and allowed to vary freely with γ-diversity [15]. Therefore, at large spatial scales, we should expect β-diversity not to be reliant on γ-diversity, and the latitudinal β-diversity patterns in such scenarios remain unknown.