A Disturbing View of Life History Evolution

Abstract

Species’ lifetime schedules of survival, growth, and reproduction generally assort along a principal axis of variation called the “fast-slow” continuum, with positions attributed to the value of producing many fragile offspring early versus few high-quality offspring later. Fast species are classically associated with surplus or pulsed resources and slow species with stable, limiting resources. Here we demonstrate that the fast-slow continuum can also emerge as a zone of highest fitness in the face of unpredictable, catastrophic demographic disturbances regardless of resource supply, competition, or life history trade-offs. Our resilience framework measures resistance, recovery, and fitness of stage-structured life histories in stochastically disturbed environments. Structured disturbances favor either fast or slow life history variants because of their respective weak resistance and fast recovery or strong resistance and slow recovery. Demographic disturbance regimes might therefore play an important role in shaping nature’s diversity of life histories. The resilience framework is a useful tool for understanding species’ demographic and evolutionary responses to environmental fluctuations and change.