Data from: Population structure and genetic diversity among eelgrass (Zostera marina) beds and depths in San Francisco Bay

The seagrass Zostera marina is widely distributed in coastal regions
throughout much of the northern hemisphere, forms the foundation of an
important ecological habitat, and is suffering population declines.
Studies in the Atlantic and Pacific oceans indicate the degree of
population genetic differentiation is location-dependent. San Francisco
Bay, California, USA, is a high-current, high-wind environment where
rafting of seed-bearing shoots has the potential to enhance genetic
connectivity among Z. marina populations. We tested Z. marina from six
locations, including one annual population, within the bay to assess
population differentiation and to compare levels of within-population
genetic diversity. Using seven microsatellite loci, we found significant
differentiation among all populations. The annual population had
significantly higher clonal diversity than the others but showed no
detectible differences in heterozygosity or allelic richness. There
appears to be sufficient input of genetic variation through sexual
reproduction or immigration into the perennial populations to prevent
significant declines in the number and frequency of alleles. In additional
depth comparisons, we found differentiation among deep and shallow
portions in one of three beds evaluated. Genetic drift, sweepstakes
recruitment, dispersal limitation, and possibly natural selection may have
combined to produce genetic differentiation over a spatial scale of 3 – 30
km in Z. marina. This implies the scale of genetic differentiation may be
smaller than expected for seagrasses in other locations, too. We suggest
that populations in close proximity may not be interchangeable for use as
restoration material.