Some communities, such as coral reefs, kelp forests, and seagrass beds may be comprised of a single dominant species, and genetic diversity within these species may play an analogous role to species diversity in more speciose systems. Through manipulative field experiments and laboratory mesocosms, we have been examining the effects of genetic diversity in the eelgrass Zostera marina on community function and stability. Field experiments show that genetic diversity enhances community resistance to natural disturbances by grazing geese and algal blooms as well as experimentally imposed disturbances. These differences in disturbance response affect the abundance of epifaunal grazers such as amphipods and other small crustaceans on seagrasses.	Top: A field experiment in the Bodega Harbor Eelgrass beds. Left: Brandt Geese moving in to graze on eelgrass. Bottom: Measuring nutrient uptake in seagrass in the lab.
In laboratory experiments we have been measuring the physiological performance of individual seagrass clones grown in common gardens. We find strong physiological differences in nutrient uptake as well as allocation to shoot vs. root biomass in which no single clone maximizes all aspects of clonal performance. This suggests there are phenotypic differences among clones that may underlie observed diversity effects in the field. Current work in this area focuses on identifying mechanisms of clonal interactions and competitive hierarchies of clones as well as interactive effects of genetic and species diversity on eelgrass ecosystem characteristics.

Relevant Papers

Hughes, A. R., and J. J. Stachowicz. 2004. Genetic diversity enhances the resistance of a seagrass ecosystem to disturbance. Proceedings of the National Academy of Sciences of the United States of America 101:8998-9002. [-pdf-]

Hughes, A. R., J. E. Byrnes, D. L. Kimbro, and J. J. Stachowicz. 2007. Reciprocal relationships and potential feedbacks between biodiversity and disturbance. Ecology Letters 10:849-864. [-pdf-]