M.S. - Botany (Ecology, Evolution and Conservation Biology)
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ItemPollination biology of Hawaiian Scaevola (Goodeniaceae)( 2008)The genus Scaevola (Goodeniaceae) occurs as shrubs to small trees in diverse habitats in Hawai'i, from coastal strand to montane rainforests. Extensive variation in floral characteristics suggests pollinators differ among species. Bees (Hylaeus spp.) and honeycreepers (Drepanidinae) are the putative native pollinators, but their diversity and abundance have declined over the last century. Due to high rates of extinction among the Hawaiian fauna and the introduction of alien generalists, former roles of some native flower visitors may remain a mystery, and the timeliness of understanding the roles of those still present is underscored. Pol1ination syndromes may offer clues regarding former pollinators that have become extinct or extirpated, or shifted to new resources. This study quantified flower visitation rates, visitor behavior, nectar volume, sugar concentration and sugar composition along with a series of structural measurements of floral display, attraction, and the mechanics of nectar access for all nine extant species of Scaevola in three lineages. Visitation was primarily diurnal, ranging from 0.2 to 3.0 visits• flower-1•hour-1 during the day, with 4-15 visitor taxa per species. Non-native visitors, mainly honey bees (Apis mellifera) and ants, were the most frequent visitors for most species. Hylaeus were infrequent visitors to three species and common only at S. chamissoniana. Birds were the main visitors to S. glabra and S. procera, with the alien Zosterops japonicus a primary visitor to both, and the native Hemignathus kauaiensis also a primary visitor to S. glabra. Visitation was often conducive to pollination for most species. Visitor interactions differed for each species of Scaevola, and in several cases may impose limitations on pollination. There were significant differences in nectar volume, concentration and most floral measurements among and within lineages (P < 0.001). Flowers ranged from small, pale, and scented ones with small amounts of sucrose-dominant nectar in high concentrations to large, heavy, decurved, and brightly colored ones lacking scent and containing copious amounts of dilute, hexose-dominant nectar. Pollination syndromes corresponded with the putative native pollinators. Nearly all Scaevola species exhibit combinations of traits suggesting generalist strategies to allow for visitation by diverse pollinator guilds. Some of these traits may indicate generalist passerine and large moth pollinator guilds that no longer exist among native visitors for some species of Scaevola. The prevalence of alien visitors has several implications for both the plants and native flower visitors. Non-native species may be depriving native visitors of floral resources and may limit plant reproduction if alien visitors are less effective pollinators than native species. Alternatively, non-native visitors may pollinate Scaevola species whose native pollinators have declined or shifted to new resources for unrelated reasons. The research presented herein provides baseline data on flower biology and flower visitation, from which future pollination investigations may be directed.
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ItemResearch on native plants for coastal wetland restoration on O'ahu(University of Hawaii at Manoa, 2003-12)Outplanting field trials were conducted to identify native wetland plant species that would be useful to coastal wetland restoration on Oʻahu. The effects of soil salinity and soil temperature, initial planting density, and removal of competition on survival and growth of outplanted species were examined. Germination response of four native wetland sedges to different water, salinity and temperature regimes was also investigated. Final survival exceeded 70 percent in four of the seven outplanted species. Soil salinity and soil temperature were negatively correlated with survival in only one species. Planting density and removal of competition had little effect on final survival and growth of outplanted species. Germination under experimental conditions exceeded 25 percent in only two of the four sedge species studied. Overall, seeds germinated to a higher percentage under lower temperatures and salinities than under higher temperatures and salinity levels. Water level had little effect on final germination percentage.
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ItemEffects of light and nutrients on the community composition of Benthic Algae in a Hawaiian stream(University of Hawaii at Manoa, 2003-08)
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ItemEffects of soil disturbance on root colonization by arbuscular Mycorrhizal Fungi and growth of native and invasive plants(University of Hawaii at Manoa, 2003-05)Experiments were conducted to determine the effects of soil disturbance on arbuscular mycorrhizal fungi root colonization and the growth of invasive and native Hawaiian plants, predicting higher AMP dependency in native species than invaders, with consequent decreased root colonization and plant growth with disturbance. Six species were grouped into 3 pairs (1 native: 1 invasive) and plants were grown in disturbed and undisturbed treatments in the greenhouse and field for 4/6 weeks. Root colonization, root length, stem and seedling height, leaf number, shoot and root biomass, and mycorrhizal dependency (MD) were measured. Root colonization was not affected by disturbance. Disturbance hindered growth of Acacia confusa, Acacia koa, Eidens pilosa, and Eidens sandvicensis. Data from only 1 pair (Acacia sp.) showed native plant MD greater than invader MD. The relationship between soil disturbance, root colonization, and plant growth may be species specific, and no native or invasive species trends were detected.