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Abstract Detail

Reproductive Processes

Deans, Susan [1], Walsh, Seana [1].

Pollination ecology of the endangered Hawaiian tree species Hibiscus waimeae subsp. hannerae (Malvaceae).

Hibiscus waimeae subsp. hannerae is a federally endangered taxon endemic to Kauaʻi, one of the eight main islands making up the Hawaiian archipelago. With possibly as few as 150 individuals persisting in the wild, recruitment failure will mean extinction unless conservation actions are taken. The Hawaiian Islands are home to many unique, codependent plant/pollinator mutualisms which, when disrupted by invasive species, can lead to the decline of one or both obligate partners. Hibiscus waimeae subsp. hannerae is a small tree with large, white, fragrant flowers that stay open throughout the night. These combined traits conform to a moth pollination syndrome. To examine whether flowers of this taxon are attracting sphingid moths, pollinator observations were carried out on cultivated individuals in the Limahuli Garden of the National Tropical Botanical Garden over a period of four months. Floral visitors were photographed or captured for identification. To evaluate the importance of pollinators for seed set, subsets of flowers were either 1) bagged to exclude pollinators, 2) hand self-pollinated, 3) hand outcross-pollinated, or 4) unmanipulated and unbagged as a control. Fruit set, seed set, seed weight, and viability were compared among treatments. All floral visitors were non-native insect and bird species, and most were nectar thieves, visiting the flower without performing the service of pollination. Resting on the pedicel, Japanese white eyes, ants, and honey bees sipped nectar from the calyx tube without coming into contact with anthers or stigmas. Honeybees also were observed foraging for pollen and contacting stigmas in the process, indicating they may be serving as novel pollinators. The most numerous, potentially legitimate visitors were crepuscular hovering moths in the Sphingidae family. At least three species of non-native sphingid moths were observed feeding at the flowers from the front, contacting the stamens and stigmatic surfaces. It remains unclear how successfully these non-native moths are transferring pollen between flowers, or if native moths are still abundant enough to be pollinators. Results from the breeding system study suggest that this species is predominately, physically self-incompatible. For this endangered species heavily reliant upon pollinators for reproduction, competition from non-native nectar thieves could threaten persistence of the species in the wild and native sphingid moths that may depend upon its nectar as a food resource.

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1 - National Tropical Botanical Garden - Kalaheo, HI, Science and Conservation, 3530 Papalina Road, Kalaheo, HI, 96741, United States

Hibiscus waimeae subsp. hannerae
moth pollination
novel pollinators
nectar thieves
breeding system

Presentation Type: Oral Paper
Session: 30, Reproductive Processes
Location: Fort Worth Ballroom 7/Omni Hotel
Date: Tuesday, June 27th, 2017
Time: 4:15 PM
Number: 30010
Abstract ID:198
Candidate for Awards:None

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