PARENT SESSION
Contributed Oral Session 122: Invasive Species: Pollination - Dispersal
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 521 A, Level 5, Palais des congrès de Montréal
Alien birds facilitate the invasion of alien plants in dry and mesic forests in Hawaii.
Chimera, Charles1, Bakutis, Ane1, Drake, Donald*,1, 1 University of Hawaii - Manoa, Honolulu, HI
ABSTRACT- Seed dispersal is a critical phase in plant population and community dynamics. On many oceanic islands, populations of native seed dispersers have been severely reduced and their functional role is now performed by alien species. We studied frugivory and seed dispersal by birds in Hawaiian dry and mesic forests. No native birds occurred in either forest, and the main seed disperser in both was the introduced Japanese White-eye, Zosterops japonicus. Even though native plants dominated the overstory of both forests, alien species contributed >90% of the bird-dispersed seed rain in each. The most abundant species in the mesic forest's seed rain was the alien shrub Clidemia hirta (1564 seeds m-2 yr-1), which occurred in 100% of the seed traps and grew in all the seedling plots. The most abundant species in the savanna-like dry forest's seed rain was the alien tree Bocconia frutescens (473 seeds m-2 yr-1 under trees and 6 seeds m-2 yr-1 in the open), which occurred in both 93% of the seed traps and 84% of the seedling plots located under trees. Fleshy-fruited, native species were poorly represented in the seed rain and some were not taken by birds at all. In general, heavy-fruiting, small-seeded alien species were overrepresented in the seed rain, and larger-seeded native species were underrepresented. Our results suggest that while alien birds may have replaced native birds as the functional seed dispersers in Hawaiian forests, their main effect may be to facilitate the spread of invasive alien plant species.
Key words: frugivory, seed dispersal, alien species, islands