An ancient eelgrass clone in the Baltic

We report that an eelgrass bed Zostera marina L. at the Aland Islands, nort hern Baltic Sea, is dominated by a. single genotype which extends over an a rea of approximately 160 x 40 m. In total, 47 individuals were sampled and genotyped for 6 highly polymorphic microsatellite loci. Forty-four of the r amets revealed the same 6-locus genotype, including 3 identical heterozygou s loci. They were thus assigned to the same genet (= clone). To our knowled ge, it represents the largest marine plant identified thus far. Based on es timates of horizontal rhizome growth rates, this clone may be more than 100 0 yr old. The remarkable phenotypic plasiticity of a single genotype which dominates this site illustrates that there is no simple one-to-one relation ship between genetic diversity and population persistence in changing and s tressful environments.