The role of avian seed dispersal on the invasion of Juniperus bermudiana in Hawaii: Facilitation or Inhibition?
Woo, Eliza*,1, 1 State University of New York, Stony Brook, NY
ABSTRACT- Studies of the factors promoting biological invasions often focus on the effects of invasive species within a single trophic level. However, successful control of an invasive species requires a clear understanding of its interactions with the community, particularly if the continual establishment and expansion of an invasive species is dependent on these interactions. My study examined the community interactions promoting dispersal of a non-native plant, Juniperus bermudiana (Bermuda Juniper) in the West Maui Mountains of Hawaii. I focused on how non-native avian seed dispersal affects the invasion establishment and spread of J. bermudiana. Field observations reveal two dominant foragers of J. bermudiana seed cones: Zosterops japonicus (Japanese White-Eye) and Cardinalis cardinalis (Northern Cardinal). These two foragers affect the invasion of J. bermudiana in opposite ways. Z. japonicus swallow J. bermudiana seed cones whole, and most likely enhance the germination of J. bermudiana seeds after digestion. C. cardinalis, on the other hand, crush J. bermudiana seed cones, and destroy any chance of germination of J. bermudiana seeds after digestion. Point counts and J. bermudiana tree watches were used to measure relative abundances and seed cone removal and visitation rates of these foragers, respectively. Field observations of the foraging behaviors of Z. japonicus and C. cardinalis on J. bermudiana seed cones provided an explanation that may explain the slow rate of spread exhibited by J. bermudiana since its introduction in the 1930s. This study demonstrated how plant-animal interactions can facilitate and/or inhibit biological invasions, and why it is important to understand these community interactions for management purposes.
Key words: Juniperus bermudiana, invasive species, avian seed dispersal, Hawaii
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