In arid ecosystems the unpredictable rainfall patterns pose a risk on reproduction. Seed germination traits of annual plants are under strong adaptive pressure to minimize the effects of loss of recruitment when water availability is scarce after germination. We studied the joint effects of unpredictable rainfall variation and resource competition on the evolutionary dynamics of the timing of germination and germination rate in a multispecies consumer-resource model, where the seasonal changes of germination traits are modeled using a function describing dormancy-nondormancy cycles. Our main focus is on how different patterns of whithin-year variation in water availability affect the evolution of germiantion traits, when there are trade-offs between the timing of germination, the length of vegetative phase and resource use efficiency. Our method is based on standard invasibility analysis and the evolutionary aspects are studied with the tools of adaptive dynamics.

Results/Conclusions

Evolutionary stable strategies, points of evolutionary diversification and evolutionarily stable coalitions are identified depending on these different scenarios and the effect of the strength of resource competition on the evolutionary outcome is analysed. We also show that after diversification the assembly of the coexisting strategies is stabilized by mechanisms that were found in classic community models of species coexistence, such as the storage effect and non-linearity of resource competition.