Date of Graduation

5-2021

Document Type

Thesis

Degree Name

Bachelor of Science

Degree Level

Undergraduate

Department

Biological Sciences

Advisor/Mentor

Beaulieu, Jeremy

Committee Member/Reader

Ungar, Peter

Committee Member/Second Reader

Alverson, Andrew

Committee Member/Third Reader

Ivey, Mack

Abstract

Within the study of invasive plants, particular importance is placed on elucidating the mechanisms by which these plants proliferate and dominate within their introduced ranges. Several theories have been advanced to explain these invasions, each with different implications for the predicted range of invasive plants. Recent studies have provided support for the application of several invasion theories to Lonicera maackii, or what is more commonly referred to as bush honeysuckle. This species provides a unique opportunity to examine the efficacy of these theories in explaining the range expansion of invasive plants. L. maackii is endemic to eastern Asia, but it has invaded much of the eastern United States, posing a serious threat to the health of forests and other natural areas. To evaluate the application of biotic and abiotic theories of invasion for L. maackii, we modeled the climatic niche space of L. maackii in both its native and invasive ranges. We visually inspected and verified 1,046 L. maackii localities and 126 L. subsessilis localities, the sister taxon to L. maackii. After associating these localities with 19 climatic variables (BIOCLIM), we performed a principal component analysis (PCA) and observed a clear separation between the climatic conditions of the native East Asian L. maackii points and the invasive North American points. The climate niches of each population group (native L. maackii, invasive L. maackii, and L. subsessilis) were significantly different, suggesting that the North American population of L. maackii occupies a different climate niche than in its native East Asian range. This separation was consistent with the predicted verses observed probable occurrence maps of North America and East Asia which we built using Maxent. This change in L. maackii’s climatic niche lends support for ecological theories of invasion that feature biotic constraints on range expansion (like the Enemy Release and Novel Weapon Hypotheses) over theories relying on abiotic climatic constraints (like the Environmental Filtering Hypothesis).

Keywords

Biogeography, Invasion Biology, Climate Niche, Lonicera maackii, Range Expansion, Ecological Theories of Invasion

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