ASSESSMENT OF GENETIC DIVERSITY OF SEAGRASS POPULATIONS USING DNA-FINGERPRINTING - IMPLICATIONS FOR POPULATION STABILITY AND MANAGEMENT

Populations of the temperate seagrass, Zostera marina L. (eelgrass), o ften exist as discontinuous beds in estuaries, harbors, and bays where they can reproduce sexually or vegetatively through clonal propagatio n. We examined the genetic structure of three geographically and morph ologically distinct populations from central California (Elkhorn Sloug h, Tomales Bay, and Del Monte Beach), using multilocus restriction fra gment length polymorphisms (DNA fingerprints). Within-population genet ic similarity (S(w)) values for the three eelgrass populations ranged from 0.44 to 0.68. The Tomales Bay population located in an undisturbe d, littoral site possessed a within-population genetic similarity (S(w ) = 0.44) that was significantly lower than those of the other two pop ulations. Cluster analysis identified genetic substructure in only the undisturbed subtidal population (Del Monte Beach). Between-population similarity values (S(b)) for all pairwise comparisons ranged from 0.4 7 to 0.51. The three eelgrass populations show significantly less betw een locale genetic similarity than found within populations, indicatin g that gene flow is restricted between locales even though two of the populations are separated by only 30 km. The study demonstrates that ( i) natural populations of Z. marina from both disturbed and undisturbe d habitats possess high genetic diversity and are not primarily clonal , (ii) gene flow is restricted even between populations in dose proxim ity, (iii) an intertidal population from a highly disturbed habitat sh ows much lower genetic diversity than an intertidal population from an undisturbed site, and (iv) DNA fingerprinting techniques can be explo ited to understand gene flow and population genetic structure in Z. ma rina, a widespread and ecologically important species, and as such are relevant to the management of this coastal resource.