Seagrasses are key habitat-forming species of coastal areas. While previous research has demonstrated considerable small-scale variation in seagrass abundance and structure, studies teasing apart local from large-scale variation are scarce. We determined how different biogeographic scenarios, under varying environmental and genetic variation, explained variation in the abundance and structure (morphology and biomass allocation), epiphytes and sexual reproduction intensity of the seagrass Cymodocea nodosa. Regional and local-scale variation, including their temporal variability, contributed to differentially explain variation in seagrass attributes. Structural, in particular morphological, attributes of the seagrass leaf canopy, most evidenced regional seasonal variation. Allocation to belowground tissues was, however, mainly driven by local-scale variation. High seed densities were observed in meadows of large genetic diversity, indicative of sexual success, which likely resulted from the different evolutionary histories undergone by the seagrass at each region. Our results highlight that phenotypic plasticity to local and regional environments need to be considered to better manage and preserve seagrass meadows.

海草是沿海地区形成栖息地的主要物种。尽管先前的研究表明海草丰度和结构发生了小规模的变化，但很少有研究使海草的丰度和结构发生局部变化。我们确定了在不同的环境和遗传变异下，不同的生物地理场景如何解释海草Cymodocea nodosa的丰度和结构（形态和生物量分配），附生植物和有性生殖强度的变化。区域和地方尺度的变化，包括它们的时间变化，有助于以不同的方式解释海草属性的变化。海草叶冠层的结构特征，尤其是形态特征，是最明显的区域季节性变化。但是，分配给地下组织的主要原因是局部尺度的变化。在具有大量遗传多样性的草地上观察到高种子密度，表明有性成功，这可能是由于每个地区海草经历的不同进化史所致。我们的结果表明，需要考虑对本地和区域环境的表型可塑性，以更好地管理和保护海草草甸。