Department of Biology, Botany Unit, University of Pisa, Pisa, Italy.
CIRSEC - Centre for Climate Change Impact, University of Pisa, Pisa, Italy.
Ann Bot. 2022 Jul 18;129(7):775-786. doi: 10.1093/aob/mcac037.
Interactions between ecological factors and seed physiological responses during the establishment phase shape the distribution of plants. Yet, our understanding of the functions and evolution of early-life traits has been limited by the scarcity of large-scale datasets. Here, we tested the hypothesis that the germination niche of temperate plants is shaped by their climatic requirements and phylogenetic relatedness, using germination data sourced from a comprehensive seed conservation database of the European flora (ENSCOBASE).
We performed a phylogenetically informed Bayesian meta-analysis of primary data, considering 18 762 germination tests of 2418 species from laboratory experiments conducted across all European geographical regions. We tested for the interaction between species' climatic requirements and germination responses to experimental conditions including temperature, alternating temperature, light and dormancy-breaking treatments, while accounting for between-study variation related to seed sources and seed lot physiological status.
Climate was a strong predictor of germination responses. In warm and seasonally dry climates the seed germination niche includes a cold-cued germination response and an inhibition determined by alternating temperature regimes and cold stratification, while in climates with high temperature seasonality opposite responses can be observed. Germination responses to scarification and light were related to seed mass but not to climate. We also found a significant phylogenetic signal in the response of seeds to experimental conditions, providing evidence that the germination niche is phylogenetically constrained. Nevertheless, phylogenetically distant lineages exhibited common germination responses under similar climates.
This is the first quantitative meta-analysis of the germination niche at a continental scale. Our findings showed that the germination niches of European plants exhibit evolutionary convergence mediated by strong pressures at the macroclimatic level. In addition, our methodological approach highlighted how large datasets generated by conservation seed banking can be valuable sources to address questions in plant macroecology and evolution.
在建立阶段，生态因素与种子生理反应之间的相互作用塑造了植物的分布。然而，由于大规模数据集的稀缺，我们对早期生命特征的功能和进化的理解受到了限制。在这里，我们使用来自欧洲植物种子保护数据库（ENSCOBASE）的综合种子保存数据，检验了温带植物的萌发生态位是由其气候需求和系统发育关系所决定的假设。
我们对来自实验室实验的 2418 个物种的 18762 个萌发测试的原始数据进行了基于系统发育的贝叶斯元分析，这些实验在欧洲所有地理区域进行。我们检验了物种的气候需求与对实验条件（包括温度、交替温度、光照和打破休眠处理）的萌发反应之间的相互作用，同时考虑了与种子来源和种子批生理状态有关的研究间变异。
气候是萌发反应的一个强有力的预测因子。在温暖且季节性干燥的气候下，种子萌发生态位包括一个由低温引发的萌发反应和一个由交替温度模式和低温层积决定的抑制反应，而在高温季节性较强的气候下则可以观察到相反的反应。种子对破皮和光照的萌发反应与种子质量有关，但与气候无关。我们还发现了实验条件下种子反应的显著系统发育信号，这表明萌发生态位受到系统发育的限制。然而，系统发育上较远的谱系在相似的气候下表现出共同的萌发反应。
这是首次在大陆尺度上对萌发生态位进行的定量元分析。我们的研究结果表明，欧洲植物的萌发生态位表现出进化趋同，这是由宏观气候水平的强烈压力所介导的。此外，我们的方法学方法强调了保护种子库产生的大型数据集如何成为解决植物宏观生态学和进化问题的有价值的资源。
