Species abundance correlations carry limited information about microbial network interactions
Fig 2
Scatter plots between the abundances of two bacterial species for different interaction mechanisms: (A) mutualism, (B) competition, (C) commensalism, (D) amensalism and (E, F) exploitative interactions. The abundances of the two species N1 and N2 at equilibrium are shown as scatterplots and have been obtained by running the two-species Lotka-Volterra model, with K1 = 1.5; K2 = 1.1; r1 = 1; r2 = 2 and αij drawn randomly from normal distributions with identical means and standard deviations (α12 ~ N(|0.7|, 0.2), α21 ~ N(|0.7|, 0.2)). In the case of commensalism and amensalism: α12 ~ N(|0.7|, 0.2) and α21 = 0. The two species can co-exist under certain combinations of αij (S1 Text). The grey polygon indicates the area where co-existence is possible. Note that the axes have different ranges in each subplot. Because the two species have different carrying capacities, the two situations of exploitative interactions are different. i.e., in case of exploitative interaction type 1: species 1 is exploited by species 2 and in case of exploitative interaction type 2: species 2 is exploited by species 1.