Genetic diversity matters for restoration of a threatened saltmarsh plant in harsh environments

While genetic diversity is theorised to increase the restoration success of degraded plant populations, previous studies examining its impacts on restoration outcomes have yielded mixed results. We hypothesise that the importance of genetic diversity for the performance of plants targeted for restoration increases with environmental stress and varies with specific plant traits related to different plant successive life stages. To test this, we conducted a fully factorial common garden experiment, crossing salinity and genetic diversity under low‐ and high‐nitrogen conditions on the growth and reproduction of Scirpus mariqueter, a threatened endemic saltmarsh plant in the Yangtze Estuary. The impacts of genetic diversity varied across stress gradients and metrics. Under high stress (high salinity, low nutrients), greater diversity enhanced reproductive traits such as clonal growth and seed production, but not under low stress. Plant growth traits showed no diversity effects regardless of stress. Synthesis: Our results highlight the importance of considering intraspecific genetic diversity in ecological restoration and help explain the context‐dependent effects of diversity. 摘要 尽管理论上遗传多样性被视为提升退化植物种群恢复成功率的重要因素，但既往关于其对恢复成效影响的研究却得出不一致的结论。 本研究假设，在植物种群恢复的过程中，遗传多样性的重要性会随环境胁迫程度的增加而提高，且这种效应会因植物的不同生长阶段而不同。为验证上述假设，本研究设计了一个同质园实验，探究在不同的胁迫条件(营养和盐度)下，遗传多样性对长江口受威胁的特有盐沼植物海三棱藨草(Scirpus mariqueter)生长和繁殖的影响。 遗传多样性对海三棱藨草的影响因胁迫程度和评估指标的变化而不同。在高胁迫条件下(高盐度、低养分)，遗传多样性提高了海三棱藨草有性和无性繁殖能力；但在低胁迫条件下，遗传多样性对于繁殖能力的影响不显著。遗传多样性对海三棱藨草生长相关性状的影响在任何胁迫条件下均不显著。 本研究强调了在生态恢复中考虑种内遗传多样性的重要性，并有助于解释多样性效应的情境依赖性。 This study investigates a critical ecological question: How genetic diversity influences vegetation restoration. Using Scirpus mariqueter, a threatened saltmarsh plant in the Yangtze Estuary, as a model species, it was revealed that higher genetic diversity enhances reproductive traits under high‐stress conditions, while growth traits remain unaffected. The findings support the stress gradient hypothesis at the intraspecific level, highlighting the context‐dependent nature of genetic diversity's role in restoration outcomes.