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Seed Dispersal & Germination by Native vs. Exotic Avian Frugivores of Hawaiʻi Island
|Title:||Seed Dispersal & Germination by Native vs. Exotic Avian Frugivores of Hawaiʻi Island|
|Contributors:||Ostertag, Rebecca (advisor)|
Tropical Conservation Biology & Environmental Science (department)
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|Date Issued:||Jun 2020|
|Publisher:||University of Hawaii at Hilo|
|Abstract:||On islands worldwide, mass avian extinctions related to anthropogenic activity have enabled exotic generalists to fill empty niches left by larger native specialists. In Hawaiʻi, this trend is prevalent; therefore, ensuring the survival Hawaiʻi’s last few native frugivores, the ʻalalā (Corvus hawaiiensis) and ʻōmaʻo (Myadestes obscurus), is integral in preserving proper seed dispersal function. Recently proposed management actions include reintroducing native frugivores into former ranges on leeward Hawaiʻi Island. This study sought to determine which native fruiting plants would benefit from native frugivore reintroductions and how exotic frugivores compare to natives in seed dispersal efficacy. I measured and compared the diet composition of two non-native, warbling white-eye (Zosterops japonicus) and red-billed leiothrix (Leiothrix lutea), and two native (ʻōmaʻo and ʻalalā) bird species. I also compared germination success of nine native fruiting plants consumed by these species. To examine diet composition and germination, I collected seeds from avian fecal samples and planted them in growth media to detect differences in gut-passage effects on germination percent and rate among avian species. I also collected avian seed rain using aerial seed traps hung above the fruiting understory to determine if avian diet and seed rain were similar in composition. ʻŌmaʻo had significantly higher diet diversity than other frugivores. Leiothrix and ʻalalā had similar but lower diversity, and warbling white-eye had the lowest diet diversity and were the least frugivorous. For germination success, the key influence was pulp-removal, by bird or hand, as there were no conclusive differences between avian gut-passage in birds and control seeds without pulp. Results showed a proportional representation of different fruits in bird diet matched that in seed rain. These results support ‘ōmaʻo and ʻalalā reintroductions as a strategy to promote dispersal of native plants and provide insight into potential changes in the native plant community composition should native frugivores go extinct and be supplanted by exotics.|
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Tropical Conservation Biology and Environmental Science|
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