Arnaud-Haond Sophie, Stoeckel Solenn, Bailleul Diane
Université de Montpellier, Ifremer, CNRS, IRD, MARBEC, Sète, France.
IGEPP INRAE, Institut Agro, University of Rennes, Le Rheu, France.
Mol Ecol. 2020 Sep;29(17):3248-3260. doi: 10.1111/mec.15532. Epub 2020 Aug 29.
Seagrass meadows are among the most important coastal ecosystems in terms of both spatial extent and ecosystem services, but they are also declining worldwide. Understanding the drivers of seagrass meadow dynamics is essential for designing sound management, conservation and restoration strategies. However, poor knowledge of the effect of clonality on the population genetics of natural populations severely limits our understanding of the dynamics and connectivity of meadows. Recent modelling approaches have described the expected distributions of genotypic and genetic descriptors under increasing clonal rates, which may help us better understand and interpret population genetics data obtained for partial asexuals. Here, in the light of these recent theoretical developments, we revisited population genetics data for 165 meadows of four seagrass species. Contrasting shoot lifespan and rhizome turnover led to the prediction that the influence of asexual reproduction would increase along a gradient from Zostera noltii to Zostera marina, Cymodocea nodosa and Posidonia oceanica, with increasing departure from Hardy-Weinberg equilibrium (F ), mostly towards heterozygote excess, and decreasing genotypic richness (R). This meta-analysis provides a nested validation of this hypothesis at both the species and meadow scales through a significant relationship between F and R within each species. By empirically demonstrating the theoretical expectations derived from recent modelling approaches, this work calls for the use of Hardy-Weinberg equilibrium (F ) rather than only the strongly sampling-sensitive R to assess the importance of clonal reproduction (c), at least when the impact of selfing on F can be neglected. The results also emphasize the need to revise our appraisal of the extent of clonality and its influence on the dynamics, connectivity and evolutionary trajectory of partial asexuals in general, including in seagrass meadows, to develop the most accurate management strategies.
就空间范围和生态系统服务而言，海草草甸是最重要的沿海生态系统之一，但它们在全球范围内也在减少。了解海草草甸动态的驱动因素对于设计合理的管理、保护和恢复策略至关重要。然而，对克隆性对自然种群群体遗传学影响的了解不足严重限制了我们对草甸动态和连通性的理解。最近的建模方法描述了在克隆率增加的情况下基因型和遗传描述符的预期分布，这可能有助于我们更好地理解和解释为部分无性繁殖体获得的群体遗传学数据。在此，鉴于这些最新的理论进展，我们重新审视了四种海草物种的165个草甸的群体遗传学数据。对比地上茎寿命和根状茎周转情况可预测，从无叶小茨藻到大叶藻、瘤状半叶马尾藻和地中海海神草，无性繁殖的影响将沿着一个梯度增加，偏离哈迪-温伯格平衡（F）的程度增加，主要朝着杂合子过剩的方向，且基因型丰富度（R）降低。这项荟萃分析通过每个物种内F和R之间的显著关系，在物种和草甸尺度上对这一假设进行了嵌套验证。通过实证证明从最近的建模方法得出的理论预期，这项工作呼吁使用哈迪-温伯格平衡（F）而不是仅使用对采样敏感的R来评估克隆繁殖（c）的重要性，至少在可以忽略自交对F的影响时如此。结果还强调，需要修订我们对克隆性程度及其对一般部分无性繁殖体（包括海草草甸中的无性繁殖体）的动态、连通性和进化轨迹影响的评估，以制定最准确的管理策略。
