Genotypic data for nine microsatellite loci for the seagrass Zostera muelleri collections from Lake Macquarie, NSW, Australia

Seagrasses are ecosystem engineers that offer important habitat for a large number of species and provide a range of ecosystem services. Many seagrass ecosystems are dominated by a single species; with research showing that genotypic diversity at fine spatial scales plays an important role in maintaining a range of ecosystem functions. However, for most seagrass species, information on fine-scale patterns of genetic variation in natural populations is lacking. In this study we use a hierarchical sampling design to determine levels of genetic and genotypic diversity at different spatial scales (centimeters, meters, kilometers) in the Australian seagrass Zostera muelleri. Our analysis shows that at fine-spatial scales (< 1 m) levels of genotypic diversity are relatively low (R (Plots) = 0.37 ± 0.06 SE), although there is some intermingling of genotypes. At the site (10's m) and meadow location (km) scale we found higher levels of genotypic diversity (R (sites) = 0.79 ± 0.04 SE; R (Locations) = 0.78 ± 0.04 SE). We found some sharing of genotypes between sites within meadows, but no sharing of genotypes between meadow locations. We also detected a high level of genetic structuring between meadow locations (FST = 0.278). Taken together, our results indicate that both sexual and asexual reproduction are important in maintaining meadows of Z. muelleri. The dominant mechanism of asexual reproduction appears to occur via localised rhizome extension, although the sharing of a limited number of genotypes over the scale of 10's of metres could also result from the localised dispersal and recruitment of fragments. The large number of unique genotypes at the meadow scale indicates that sexual reproduction is important in maintaining these populations, while the high level of genetic structuring suggests little gene flow and connectivity between our study sites. These results imply that recovery from disturbances will occur through both sexual and asexual regeneration, but the limited connectivity at the landscape-scale implies that recovery at meadow-scale losses is likely to be limited.

海草（seagrass）是生态系统工程师（ecosystem engineers），可为大量物种提供关键栖息地，并提供多样的生态系统服务。多数海草生态系统由单一物种占优；已有研究表明，精细空间尺度下的基因型多样性（genotypic diversity）在维持一系列生态系统功能中发挥着重要作用。然而，对于多数海草物种而言，其自然种群中精细尺度遗传变异（genetic variation）模式的相关信息仍较为匮乏。本研究采用分层抽样设计（hierarchical sampling design），以探究澳大利亚海草物种穆氏大叶藻（Zostera muelleri）不同空间尺度（厘米、米、千米）下的遗传多样性与基因型多样性水平。分析结果显示，在精细空间尺度（<1米）下，基因型多样性水平相对较低（样方R值=0.37±0.06标准误（SE）），尽管存在一定程度的基因型混合现象。在样地（10米级）与海草床分布区（千米级）尺度下，我们检测到的基因型多样性水平更高（样地R值=0.79±0.04标准误；分布区R值=0.78±0.04标准误）。我们发现海草床内部的不同样地间存在部分基因型共享，但海草床分布区间无基因型共享现象。我们还在海草床分布区间检测到了高水平的遗传结构分化（FST=0.278）。综合来看，本研究结果表明，有性生殖与无性生殖均对穆氏大叶藻海草床的维持发挥着重要作用。无性生殖的主要机制似乎为局部根茎延伸，不过在10米级尺度下存在的少量基因型共享现象，也可能源于片段的局部分散与定植。海草床尺度下存在大量独特基因型，这表明有性生殖对该种群的维持至关重要；而高水平的遗传结构分化则说明本研究样地间的基因流与连通性极低。上述结果表明，海草床受干扰后的恢复将同时通过有性与无性再生实现，但景观尺度下有限的连通性意味着海草床局地消亡后的恢复过程可能极为有限。