Abstract
Plants often respond to drier climates by slow evolutionary adaptations from fast-growing to stress-tolerant species. These evolutionary adaptations increase the plants' resilience to droughts but involve productivity losses that bear on agriculture and food security. Plants also respond by spatial self-organization, through fast vegetation patterning involving differential plant mortality and increased water availability to the surviving plants. The manners in which these two response forms intermingle and affect productivity and resilience have not been studied. Here we ask: can spatial patterning inhibit undesired evolutionary adaptation without compromising ecosystem resilience? To address this question, we integrate adaptive dynamics and vegetation pattern-formation theories and show that vegetation patterning can inhibit evolutionary adaptations to less productive, more stress-tolerant species over a wide precipitation range while increasing their resilience to water stress. This evolutionary homeostasis results from the high spatial plasticity of vegetation patterns, associated with patch thinning and patch dilution, which maintains steady local water availability despite decreasing precipitation. Spatial heterogeneity expedites the onset of vegetation patterning and induces evolutionary homeostasis at an earlier stage of evolutionary adaptation, thereby mitigating the productivity loss that occurs while the vegetation remains spatially uniform. We conclude by discussing our results in a broader context of evolutionary retardation.