Salt marshes are among the most biologically interesting places on earth. The waters and soil teem with plants and animals bound up in the cycles of life and death. For herbivores, salt marshes are a garden of delights, a salad bar with savory selections.
Herbivores can, however, be picky eaters depending on how palatable salt marsh plants are. New research by the University of Georgia's Marine Institute here, in collaboration with Brown University in Providence, R.I., strongly suggest that salt marsh plants nearer the equator are less palatable to herbivores than ones considerably farther away. It is the first time such a preference by herbivores for northern versus tropical plants has been conclusively demonstrated.
"There has long been a biogeographic theory that the pressure of predators and prey defenses is greater in the tropics than in higher latitudes," said Dr. Steven Pennings, an assistant research scientist at the Marine Institute. "But there hasn't been much work examining similar patterns in plant communities."
Pennings collaborated on the research with Mark Bertness and Erin Siska of Brown University. Their work was presented today at the 84th annual meeting of the Ecological Society of America in Spokane, WA. The research was supported by a grant from the National Geographic Society.
The researchers selected 10 salt marsh plants common to the Northeast coast (Maine and Rhode Island) and Southeastern sites in Georgia and Florida. These plants make up more than 85 percent of total plant biomass in all the marsh zones under study. Plant material from Rhode Island was collected, packed on ice and immediately flown to Sapelo Island, where it was exposed to a group of herbivores on the same day.
Likewise, southern plants were flown to Rhode Island in the same manner for use
with northeastern herbivores. Leaf beetles, grasshoppers, moth larvae and crabs
were used to test palatability of the plants. In all cases, the herbivores
Contact: Steven Pennings
University of Georgia