Data from: Life history costs make perfect sprouting maladaptive in two herbaceous perennials

1.Why some herbaceous plant species refrain from sprouting in some years is a longstanding puzzle in plant ecology. When vegetatively "dormant", the plant lives as a rootstock, but does not produce or maintain photosynthetic tissue. During this time, energy may be remobilized from resource reserves, or acquired from mycorrhizal fungi, although the mechanisms are still poorly understood. If vegetative dormancy is adaptive, it may be in response to a harsh environment, to life history costs, or as a bet-hedge against unpredictable environmental variability. 2.We tested whether vegetative dormancy is adaptive via game theoretical analysis of deterministic and stochastic ahistorical and historical life history models parameterized with long-term census data for two long-lived plants, Anemone americana and Cypripedium parviflorum. The ahistorical deterministic model provided a test of the hypothesis that dormancy is adaptive in response to a generally harsh environment and/or short-term life history costs, while the historical model tested whether long-term costs drove the evolution of dormancy. The stochastic ahistorical model provided a test of whether dormancy is a bet-hedging trait. 3.We found that vegetative dormancy is an adaptive consequence of life history costs of growth to survival, and that these costs may be operating under a variable but generally harsh environment. Such costs led to sprouting and survival probabilities that generally increased with size in adults but never reached unity, and decreased with size in juveniles. Historical deterministic models particularly predicted observed sprouting frequencies, while deterministic ahistorical and stochastic models did not, suggesting although the environment is likely stressful and fluctuates between harsh and mild states, short-term costs and temporal stochasticity alone do not explain observed sprouting frequencies. 4.Synthesis. Life history costs can drive the evolution of seemingly paradoxical traits. In particular, growth can lead to survival costs that may become significant in future years. These costs may be incurred via the use of stored reserves that, once used, cannot be used in the next several years. Such costs are the currency favoring the evolutionary maintenance of vegetative dormancy in two distantly related perennial plant species, and may account for dormancy throughout the Plant Kingdom.

1. 为何部分草本植物物种会在某些年份停止萌发，是植物生态学领域长期存在的未解之谜。当植物处于营养休眠状态时，仅以根状茎存活，不会产生或维持光合组织。在此期间，能量可从资源储备中重新调动，或从菌根真菌处获取，但其具体机制仍不甚明晰。若营养休眠具有适应性，则可能是对恶劣环境的响应、生活史代价的体现，或是针对不可预测环境波动的风险对冲策略。2. 我们通过博弈论分析，对两类长寿植物——美洲银莲花（Anemone americana）与小花杓兰（Cypripedium parviflorum）的长期野外普查数据进行参数化，构建了确定性、随机性的无历史及有生命史历史模型，以此检验营养休眠是否具有适应性。其中，无历史确定性模型用于检验“休眠是对整体恶劣环境和/或短期生活史代价的适应性响应”这一假说；有历史模型则用于检验长期代价是否驱动了休眠的演化；随机性无历史模型则用于检验休眠是否属于风险对冲性状。3. 研究结果表明，营养休眠是生长至存活的生活史代价带来的适应性结果，且这类代价可能在多变但整体恶劣的环境中发挥作用。此类代价会导致成株的萌发与存活概率随体型增大而普遍升高，但始终无法达到100%；而幼株的萌发与存活概率则随体型增大而降低。历史确定性模型尤其能匹配观测到的萌发频率，而确定性无历史模型与随机性模型则无法做到这一点，这提示尽管环境大概率处于胁迫状态且在恶劣与温和状态间波动，但仅依靠短期代价与时间随机性无法解释观测到的萌发频率。4. 总结：生活史代价可驱动看似矛盾的性状演化。具体而言，生长会带来存活代价，这类代价在未来数年可能变得显著。此类代价可通过储存资源的消耗产生——一旦资源被消耗，后续数年将无法再次利用。这类代价正是促使两类远缘多年生植物演化并维持营养休眠的核心因素，也可能是整个植物界中休眠现象普遍存在的原因。