The ability of plants to avoid conditions that render them vulnerable to extinction is foundational to the maintenance of diversity. In variable environments, dormancy – the production of environmentally resistant forms that can emerge when conditions improve – is a critical life history strategy that allows species to persist during unfavorable periods. Habitats have different baselines of environmental variation, which should impact the propensity of plants to enter and emerge from dormant states, yet, to date, geographic patterns in the sensitivity of plants to environmental cues remains unknown.
In this global meta-analysis, we synthesize experiments that have tested the sensitivity of dormant seeds to germination cues by compiling data from experiments that tested the role of environmental conditions for the termination of dormancy. In total, we extracted the raw data from 70 studies that included 326 species across 104 plant families from around the world, then ran a mixed-model analysis using the “metafor” package in R. We hypothesized that regions with higher environmental variability would correspond to greater dormancy rates.
Results/Conclusions
Our results revealed that dormancy rates are greater in extreme environments that exhibited high variability in temperature and precipitation (p<0.0001), specifically polar and arid sites. At the same time, other life-history characteristics explained biogeographic patterns in dormancy dynamics. Plants that exhibited physical dormancy had the highest rates of dormancy (significant dormancy type*variability interaction, p<0.0001), while perennial dormancy showed a weak and sometimes absent relationship with variation in environmental conditions.
This is the first global synthesis of extant dormancy research to consider how the sensitivity of plants to germination cues is linked to environmental variability and dormancy. By testing the role of environmental variability on the sensitivity of seeds to environmental conditions, we provide compelling empirical evidence for theoretical bet-hedging predictions, while clarifying how the nature of the dormancy response can be contingent on other life-history characteristics that themselves impact survival. The results of this work suggest that the role of dormancy for coexistence is elevated extreme environments.