Figure 16.9 Species competing for multiple resources. In the experiment, two species of diatoms compete for silicon and phosphorus. Cyclotella is more limited by a low abundance of phosphorus whereas Asterionella is more limited by a low abundance of silicon. (a) When raised under a low ratio of Si/P, Cyclotella dominates the competitive interaction. (b) When raised under an intermediate ratio of Si/P, neither species dominates. Instead, the two species coexist. (c) When raised under a high ratio of Si/P, Asterionella dominates the competitive interaction.

Data from D. Tilman, Resource competition between planktonic algae: An experimental and theoretical approach, Ecology 58 (1977): 338–348.