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Dissertation/Thesis Abstract

Pollination ecology of Broussaisia arguta (Hydrangeaceae) in a fragmented forest on the Island of Hawai'i
by Phifer, Colin, M.S., University of Hawai'i at Hilo, 2012, 75; 1511565
Abstract (Summary)

Habitat fragmentation is a leading threat to biodiversity that can impact existing plant populations as well as future recruitment by affecting pollinator community structure and pollination rates. Previous research suggests that self-incompatible plant species should be most susceptible to the effects of fragmentation. To better understand the relationship between habitat fragmentation and pollinator-mediated reproductive success, I contrasted the pollinator communities and floral visitation rates of kanawao (Broussaisia arguta , Hydrangeaceae), a common dioecious species, in a naturally fragmented forest and a nearby continuous forest on the Island of Hawai'i over two flowering seasons. I also estimated plant reproductive success across the system through quantification of seed germination (2010) and pollen tube density (2011) of open-pollinated flowers, and estimated the strength of pollen limitation through supplemental hand-pollinations with excess pollen. In 2010, honeybees were the dominant pollinators in the forest and nearly absent from the fragments where moths were the principal pollinators; pollinator visitation rates were low and not different between fragments and continuous forest. In 2011, honeybees were absent in the forest, but moths were again the dominant pollinator in the fragments. Overall visitation rates were lower than in 2010 and the rate of visitation was higher in the fragments. Seed germination results in 2010 showed that plants in medium-sized fragments had lower reproductive success than plants in the small and large fragments, which had seed germination rates similar to those of continuous-forest plants. In contrast, pollen tube densities were intermediate to high for all maternal plants in the fragments in 2011. Pollen limitation was common across the study system, though with considerable variation among plants. In conclusion, fragmentation appears to have impacted kanawao by altering pollinator communities with considerable variation in the visitation rates between the years. The two measures of reproductive success—seed germination in 2010 and pollen tubes in 2011—conflict with one another, which may by the result of an observed drought effect in 2010 or low pollinator efficiency in the medium-sized fragments. Alternatively, pollen tubes may not be an adequate surrogate for reproductive success for kanawao. The spatial and temporal variation in pollinator communities observed in this study demonstrate the need for longer-term studies and the need to understand pollinator movements in fragmented landscapes.

Indexing (document details)
Advisor: Stacy, Elizabeth
Commitee: Giardina, Christian, Price, Jonathan
School: University of Hawai'i at Hilo
Department: Tropical Conservation Biology & Environmental Science
School Location: United States -- Hawaii
Source: MAI 50/06M, Masters Abstracts International
Subjects: Plant biology, Ecology
Keywords: Broussaisia arguta, Forest ecology, Habitat fragmentation, Hawaii, Pollination
Publication Number: 1511565
ISBN: 978-1-267-37140-9
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