Fig 1.
Coexistence of two strains in a boom and bust environment supplied with a single limiting resource.
(a) Strains A and B follow Monod’s law of growth. Strain A is a K-strategist with a lower maximum growth rate gmax and substrate affinity(K) compared with strain B, which is an r-strategist. (b) Schematic of the serial dilution experiment. At the end of each cycle, we dilute the population by a factor D, and supply fresh medium with resource concentration c0 (see Methods). (c) Feasible environmental parameters for two strains with given growth rates. Each point on the heatmap defines an environment, characterized by c0 and D, and the color of each cell represents the relative abundance of strain B at steady state. Black lines show the range of environments where both strains, A and B, coexist. (d) Coexistence region in terms of growth parameters of strain B for a fixed environment (D = 10, c0 = 10) and fixed strain A. The blue region represents the range of growth parameters of B (red dot) where it can coexist with strain A (blue dot) in a fixed environment. Black solid lines are theoretical boundaries of the region.
Fig 2.
Three-strain coexistence in a boom and bust environment on a single resource.
(a) Growth rate profiles of strains A, B and C, which all obey Monod growth. We fixed the parameters gmax and K for strains A (blue) and B (red), and varied them for strain C in a manner that both gC and KC remained between those of strains A and B. (b) Heatmap showing the steady state community diversity (number of coexisting strains) as a function of the growth parameters gC and KC. In the region above the solid blue line, A goes extinct, above the red line, B goes extinct. The yellow dots represent 4 variants of C corresponding to 4 qualitatively distinct steady state community compositions, shown as stacked bar plots of relative abundances in (c).
Fig 3.
Communities in multi-resource environments.
Panels (a)(c)(e) show results from single species in a single resource environment, and (b)(d)(f) depict results from 2 species in a 2-resource environment. (a)-(b) Schematic of strain pool simulations. All randomly generated strains from each species are presented together at the beginning of each serial dilution simulation, which will reach a final community composition at steady state. (c)-(d) Examples of strains in a strain pool. Dots show the gmax and K’s of each strain, where the deep-colored ones represent the strains that survive in the final community. Blue dots are strains from species I and red from species II. Pie charts in (d) show the co-utilization profiles of each species. (e)-(f) Histograms of the number of survivors in the final community. Bar plots of blue and red show correspondingly the number of surviving strains from species I and II. Heatmap in (f) separately represents the joint distribution of the number of survivors in both species.