Distributions of observed interactions
(A) Interactions between a “focal” isolate and “interactor” isolate were calculated as two measures, 1) a population effect, calculated as the ratio of the focal isolate’s density with and without the interactor present, and 2) a per-capita effect, calculated as the change in density of the focal isolate between contexts with and without the interactor, scaled by the abundance of the interactor. Interactions were always calculated between communities, varying by a single isolate – the interactor. However, additional isolates (“background” isolates) could also be present in the compared communities. The “richness context” of an interaction refers to the richness of the pairs of community contexts from which an interaction is observed (e.g., 1=>2 for the first example interaction, 2=>3 for the second example interaction including a “background” isolate).
(B) The distribution of all observed interactions, as population level effects, (natural-log transformed to symmetrize ratios).
(C) The distribution of all observed interactions, as per-capita effects. In B and C, the dotted black line marks 0, and the dashed green line marks the median respective interaction (natural-log transformed for the population level effects).