Tree seedling recruitment is thought to be an important factor influencing forest 
composition and structure. In this dissertation I explore three factors that contribute to 
seedling survival at Palmyra Atoll in the Central Pacific Ocean: 1) how an invasion of 
alien rats {Rattus rattus) has influenced seed dispersal and survival, and seedling survival, 
2) how invasive coconut palms (Cocos nucifera) impact native tree reproduction and 
growth, and 3) movement patterns of five species of land crabs. I found that rats altered 
patterns of tree seedling recruitment by increasing the frequency of predation on tree 
seeds and seedlings, and by shifting local tree seed dispersal from an interaction driven 
by land crabs to a directed dispersal model driven by rats. At Palmyra, introduced rats 
surpass crabs in the frequency of herbivore-seedling interactions, and rat impacts on 
seedling survival may be responsible for the structure of the atoll's current forest 
community. Invasive coconut palms {Cocos nucifera) also appear to negatively influence 
the reproduction and possibly the growth of other tree species through canopy 
dominance. The combined impact of rats and coconut palms has been, and continues to 
be a major factor shaping Palmyra's forest community. Crabs have been previously 
overlooked in studies of tropical forest ecology. This research reinforces the roll of crabs 
as integral components of terrestrial systems on tropical, oceanic islands, and strengthens 
our understanding of how rats, as biological invaders, can have significant, lasting 
impacts on small island plant communities. 
 
Tree seedling recruitment is thought to be an important factor influencing forest 
composition and structure. In this dissertation I explore three factors that contribute to 
seedling survival at Palmyra Atoll in the Central Pacific Ocean: 1) how an invasion of 
alien rats {Rattus rattus) has influenced seed dispersal and survival, and seedling survival, 
2) how invasive coconut palms (Cocos nucifera) impact native tree reproduction and 
growth, and 3) movement patterns of five species of land crabs. I found that rats altered 
patterns of tree seedling recruitment by increasing the frequency of predation on tree 
seeds and seedlings, and by shifting local tree seed dispersal from an interaction driven 
by land crabs to a directed dispersal model driven by rats. At Palmyra, introduced rats 
surpass crabs in the frequency of herbivore-seedling interactions, and rat impacts on 
seedling survival may be responsible for the structure of the atoll's current forest 
community. Invasive coconut palms {Cocos nucifera) also appear to negatively influence 
the reproduction and possibly the growth of other tree species through canopy 
dominance. The combined impact of rats and coconut palms has been, and continues to 
be a major factor shaping Palmyra's forest community. Crabs have been previously 
overlooked in studies of tropical forest ecology. This research reinforces the roll of crabs 
as integral components of terrestrial systems on tropical, oceanic islands, and strengthens 
our understanding of how rats, as biological invaders, can have significant, lasting 
impacts on small island plant communities. 
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