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Date of Award

3-26-2019

Document Type

Thesis and Dissertation-ISU Access Only

Degree Name

Master of Science (MS)

Department

School of Biological Sciences

First Advisor

Victoria A. Borowicz

Abstract

The refuge-mediated apparent competition hypothesis (RMACH) posits that a plant species can indirectly reduce growth of competitors, and thus invade, by providing refuge for herbivores of more palatable surrounding plants. If the RMACH applies to Lespedeza cuneata, an invasive legume with dense, chemically defended foliage, I predict (a) more arthropods where the invasive is present, indicating that it provides more suitable habitat, (b) greater herbivory on plants surrounding the invasive than on the invasive itself, indicating it is not a food source, and (c) reduced herbivory on neighboring plants where the invasive has been removed. Removal of L. cuneata from experimental plots produced no overall effect on arthropod abundance; however, Japanese Beetles, a devastating invasive, were twice as abundant in plots with L. cuneata, indicating that Japanese Beetles prefer plots with L. cuneata (prediction a). L. cuneata removal did not significantly affect percent herbivory of potted native plants (“phytometers”) placed in plots to evaluate herbivory, however, L. cuneata phytometers had significantly higher total herbivory than native phytometers. These herbivory analyses do not support predictions (b) and (c): L. cuneata had higher herbivory than native species and there was no effect of L. cuneata removal on herbivory of native species. L. cuneata phytometers were very immature when placed in field plots, potentially before developing chemical defenses to deter herbivores. L. cuneata and Japanese Beetles may interact to mutually facilitate their invasion, whether it is through refuge-mediated apparent competition or another mechanism of invasion.

Comments

Imported from ProQuest Fowler_ilstu_0092N_11425.pdf

DOI

http://doi.org/10.30707/ETD2019.Fowler.J

Page Count

51

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