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Title: Impact of Alien Slugs on Native Plant Seedlings in a Diverse Mesic Forest, O'ahu, Hawai'i, and a Study of Slug Plant Food Preferences 
Author: Joe, Stephanie Marie
Date: 2006
Publisher: University of Hawai'i at Manoa
Abstract: Introduced species have the potential to cause serious ecological disruption,
particularly on oceanic islands. When introduced species invade natural areas,
endemic species may be threatened, especially when the invasive species
represent guilds or functional groups that were previously lacking. Hawai‘i has no
native slugs, but over a dozen species are now established. Slugs are important
seedling predators in their native habitats, and in introduced habitats they can
cause major shifts in the abundance some plant species. In order to better
investigate slug impacts on native plants in Hawai‘i, I carried out research which
1. identified differences in the acceptability of five native plant species to five
alien slug species 2. assessed the effect of slug herbivory on the growth and
survival of three native and two alien plant species, and 3. measured changes in
seedling regeneration due to slug herbivory.
Results from feeding assays indicated a significant difference in palatability
among plant species, but no statistical difference in overall feeding preference
among slug species. Urera kaalae (Urticaceae) was found to be significantly
more palatable than the other four plant species and, thus, is predicted to be
more vulnerable to slug herbivory in the field.
I tracked the fate of planted seedlings and natural germinants from the seed bank
in both slug-excluded and slug-accessible plots in diverse mesic forest in the
Wai‘anae Mountains on the island of O‘ahu. Among seedlings that survived to
the end of the experiment, there was no significant difference between slug herbivory
treatments in growth index measurements. There was little germination
from the seed bank, with no statistical difference in total number of seedlings
between treatments. However, two of the three native species, Schidea obovata
(Caryophyllaceae) and Cyanea superba (Campanulaceae) had significant
reductions in survival of 49% and 53%, respectively, in the slug-exposed
treatment. Survival of two invasive species, Clidemia hirta (Meslastomataceae)
and Psidium cattleianum (Myrtaceae) was not significantly affected by slugs. This
study demonstrates that slugs may pose a serious threat to native plant species
by reducing their survival and thereby facilitate the success of certain invasive
Description: viii, 87 leaves Thesis (M.S.)--University of Hawaii at Manoa, 2006. Includes bibliographical references (leaves 78-87). Also available via World Wide Web
Pages/Duration: vii, 87 leaves, bound ill., maps 29 cm
Rights: All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Keywords: Slugs (Mollusks) -- Hawaii -- Oahu

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Restricted for viewing only M.S.Q111.H3_4061_r.pdf 5.138Mb PDF View/Open
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