Coexistence in Disturbance-Prone Communities: How a Resistance-Resilience Trade-Off Generates Coexistence via the Storage Effect.

We investigate the effects of disturbance on species coexistence using a general mathematical model. The model can be applied to a variety of communities, and we show how it applies in particular to communities of shrubs in Mediterranean heathlands. Our analysis demonstrates that when species have distinct fire response strategies, disturbance allows for stable species coexistence. Furthermore, we show how the size of the coexistence region depends on fire frequency and dispersal ability. The stabilizing mechanism is classified as the spatial storage effect, which is identified by the covariance between environmental and competitive responses. This is the first time that disturbance, defined as a fluctuating mortality factor, has been definitively shown to promote coexistence via the storage effect. Moreover, we show that the biological driver is a trade-off between resistance and resilience to disturbance. The resistance-resilience trade-off is a biological mechanism of coexistence under patchy disturbance. However, the resistance-resilience trade-off has not previously featured in mathematical models of species coexistence. Although the storage effect depends on fluctuations in life-history parameters presumed to result from environmental variation, rarely are life-history parameters explicitly linked to environmental phenomena. Here the link is clear and concrete, allowing better definition of the intended application.