Figure 1.

(a) Observed (i,ii) and predicted (iii) relationships involving interaction strength, FU and number of trophic links. (b) Flow diagram highlighting the data employed to calculate FU and interaction strength. The FU of species i, FU_i, is calculated as FU_i = d_i•/d_••, where, d_i• = Σ_jd_ij, d_•• = Σ_jd_i• and d_ij is the measure of functional trait dissimilarity between species i and species j used by Pavoine et al. [7]. Interaction strength is calculated as a_ij = −b × (M_j^−0.25/s_j), where M_j is the body mass of predator j, s_j is the number of prey species consumed by predator j and the exponent of −0.25 is based on allometric scaling relationships to approximate basal metabolic rate per unit biomass. Note the interdependence of the two measures on body size, which also suggests a probable relationship. See electronic supplementary material for a more detailed description of these two measures.