Microsatellite loci in eelgrass Zostera marina reveal marked polymorphism within and among populations

Using an enriched genomic library, we developed seven (CT)(n)/(GA)(n) micro satellite loci for eelgrass Zostera marina L. Enrichment is described and h ighly recommended for genomes in which microsatellites are rare, such as in many plants. A test for polymorphism was performed on individuals from thr ee geographically separated populations (N = 15/population) and revealed co nsiderable genetic variation. The number of alleles per locus varied betwee n five and 11 and the observed heterozygosities for single loci ranged from 0.16 to 0.81 within populations. Mean allele lengths were markedly differe nt among populations, indicating that the identified loci will be useful in studying population structure in Z. marina. As the frequency of the most a bundant multilocus genotype within populations was always < 1%, these loci have sufficient resolving power to address clone size in predominantly vege tatively reproducing populations.