a) Results of one-sample t-tests (mu = 0) examining the difference between observed biomass in mixtures and the expected biomass based on biomass production in monocultures by target rarity level.

A significant divergence of standardized interaction strength from the null demonstrates that biomass in mixtures are significantly different than the expectation in monocultures. b) Results of linear mixed model examining the effects of categorical interacting rarity level (1–7 and common), continuous phylogenetic distance, and mean adult height on standardized interaction strengths. Alpha = 0.05.