Publication Date

2021

Document Type

Dissertation/Thesis

First Advisor

Jones, Holly P.

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Biological Sciences

Abstract

Islands support the greatest numbers of endemic species but are highly vulnerable to human activities. In particular, the introduction of invasive, predatory mammals (e.g., rodents) has resulted in sharp declines of island fauna due to a lack of evolved behavioral capacities to avoid depredation. Because of this, invasive species are considered to be one of the most detrimental impacts to biodiversity. To combat this biodiversity loss, the eradication of invasive mammals is now a primary conservation tool, with > 700 attempts globally. However, mammal eradications are predicated on the assumption that islands will naturally return to their pre-invaded condition. Yet many restored islands differ from their uninvaded counterparts, partly due to innate behaviors (e.g., philopatry) of highly mobile, keystone species which can limit dispersal to restored islands in the first place. Even when dispersal to restored islands is successful, the process of community reassembly may lead to an entirely different community due to variability in colonization rates and interactions between species, such as competition. The partitioning of limited resources based on behavioral adaptations or phenotype can lead to niche specialization, enabling the coexistence of closely related species. Despite the key potential for competition to shape community assemblages, there have been few opportunities to observe how these processes unfold as colonizing species reassemble into communities, especially so for vertebrates. One way to measure niche specialization is through examining species’ performances as they relate to differing resources across varying ecological conditions. Traditionally, this is done by quantifying a species’ niche breadth, or the extent of resources used by the species, and comparing the overlap of resources used between species; those species with limited niche breadth are considered to be specialized, and little niche overlap can be indicative of competitive exclusion. More recent perspectives of resource use have found differences in niche specialization between populations and even individuals. Seabirds are essential to functional island ecosystems. By connecting intertidal, marine, and terrestrial communities, they are integral components of food webs and act as island ecosystem engineers through the provisioning of nutrient subsidies, which promotes biodiversity. Aotearoa New Zealand supports the greatest number of endemic bird species; but through both European and Polynesian expansion, multiple mammalian species have been introduced to a majority of Aotearoa’s islands. Mammal eradication, initiated in the early 1900s, has led to > 100 islands that are in some form of recovery, providing a series of islands in different stages of recolonization by the world’s largest share of endemic seabird species. This is a unique opportunity to examine factors driving ecological recovery that will improve management strategies globally. The objectives of my doctoral research are to: (1) quantify changes to seabird communities due to invasive species introductions and assess whether eradication and active restoration are sufficient to promote recovery; (2) identify if and to what extent seabirds may compete for nesting space at post-eradication islands; and (3) assess model transferability to understand changes during passive island recovery.

Extent

120 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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Text

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