Fruit-eating vertebrates have experienced steep declines in abundance and diversity in many of the tropical forests in Asia, Africa, and South America. Many of the tropical trees that need high light to grow from seeds to adults depend largely on these vertebrates to carry their seeds to new openings, or gaps, in the forest created by treefalls. This project will investigate whether the disappearance of fruit-eating vertebrates is reducing the abundance of these trees and causing forest gaps to persist and accumulate. To test this, researchers will compare forests on the island of Guam, which has lost nearly all its fruit-eating vertebrates due to the introduction of a predatory snake, and on three nearby islands that retain native, fruit-eating, forest birds and, in one case, a native, fruit-eating bat. Studies will measure the dynamics of forest gaps on the islands, compare the light requirements of 16 common tree species, and test the effects of experimentally preventing dispersal of seeds on islands that do have birds.
This research will directly aid state and federal agencies to manage and restore tropical forests on Guam. Results should also be of use to managers of other tropical forests, since many pioneer species in the tropics are dispersed by vertebrates, and enlarge our understanding of the potential environmental consequences of introducing species to new areas. The project will provide scientific training for Pacific Islanders and run a special, three-week course in island ecology for students from local colleges.
