The paper compares a generalised consumer-resource model under two supply functions — logistic self-renewal vs. constant external influx — with matched consumer/resource statistics (M=S=150, 20 simulated communities per phase-diagram cell, Lyapunov-exponent stability classification). Reported results: (1) as reciprocity ρ decreases or heterogeneity σ increases, the self-renewing model passes through stable → chaotic → infeasible phases; (2) the externally-supplied model stays stable across a much larger ρ–σ region and transitions directly from stable to infeasible with no robust chaotic phase (apparent chaos near the boundary was attributed to finite-size effects requiring extreme fine-tuning) ; (3) a cavity-method derivation yields the unified condition ρ² > (S*/M)·⟨χ_R²⟩/⟨χ_R⟩², which reduces to the known self-renewing condition ρ² > S*/M* and shows externally-supplied resources cannot go extinct, so ⟨χ_R²⟩/⟨χ_R⟩² = 1 rather than M/M* ; (4) in a hybrid model, increasing influx eliminated chaos at Iα ≥ 10⁻², exactly where sensitivity of near-extinction resources to depletion ⟨(dRα/dCα)²⟩ became undetectable (n=80 communities, 95% CIs) .
Schematic ordering of the reported boundary ρ values [0.85, 0.85, 0.8, 0.75, 0.7, 0.55, 0.4] against decreasing influx; the dashed line marks the reported chaos-elimination threshold Iα = 10⁻². Values are as reported in the paper; the y-axis arrangement is for clarity, not an exact re-plot of Fig. 3B.
Strengths: The derivation is rigorous and self-consistent — the unified condition recovers the known self-renewing result, matches numerical phase diagrams (SI Fig. S1), and correctly explains why prior studies claiming supply-independence reached the opposite conclusion (they fixed surviving sets a priori, implicitly fixing susceptibilities) . Code is fully released (github.com/JamilaRowlandChandler/CRM-Resource-supply-vs-Stability).
Limitations and blind spots: (1) All results are in silico with Gaussian random parameter sampling — no empirical validation; (2) the no-chaos claim is established mainly in the large-M thermodynamic limit, and the paper itself notes finite-size chaos can be fine-tuned into existence, so the sharp dichotomy may soften at realistic community sizes; (3) the authors candidly note that persistent fluctuations observed experimentally under external supply contradict their prediction, and they speculate alternative mechanisms (pH modification, direct interactions, periodic/serial-dilution supply) without testing them ; (4) cross-feeding and community-dependent influx — acknowledged as future work — could alter the susceptibility distribution and hence the stability boundary, so generality beyond the three tested supply functions is hypothesized, not shown. Ad-hoc analysis choices (extinction threshold 10⁻⁴, peak-detection thresholds, 15 bins) were reported transparently but are not robustness-tested. BGPT inference (flagged as inference): the mechanism hinges on a bimodal susceptibility distribution; if real microbial communities have smoothly varying susceptibilities, the stable-region expansion may be smaller than predicted. What would change the conclusion: a large, controlled simulation (or experiment) showing a broad, robust chaotic phase under constant external influx, or empirical measurement showing near-extinction resource sensitivities remain high at high influx.
Clearly labeled simulated illustration: assumes the reported mechanism (sensitivity drops orders of magnitude as Iα rises to ≥10⁻²) with illustrative exponential decay and arbitrary uncertainty bands; units arbitrary until empirically anchored.
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