Date of Award

Spring 5-15-2015

Author's School

College of Arts & Sciences

Author's Program


Degree Name

Bachelor of Arts (A.B.)




While few introduced exotic species become invasive, this small number of species poses serious threats to biodiversity, ecosystem function, and recreation, leading ecologists to study why certain species become invasive and why certain communities are prone to invasions. Several leading hypotheses seek to explain invasiveness, including the Enemy Release Hypothesis, the trait superiority hypothesis, and the Biotic Resistance Hypothesis, but none are consistently supported in the literature. We suggest that the lack of uniting hypothesis is a result of the inability to put multiple proposed mechanisms in the same framework, and suggest for a uniting framework Darwin’s Naturalization Hypothesis along with a mechanistic approach and a view of multiple spatial scales. We address this by conducting an experimental study seeking the response of the effect of a competitor reduction treatment to phylogenetic novelty for native and invasive species over local and regional scales. We address (1) whether phylogenetic novelty correlates with high competitive ability, (2) if and how this relationship differs when novelty is assessed at regional versus local spatial scales, and (3) how this mechanism differs between native and invasive species. We find a significant negative correlation between phylogenetic novelty and effect of competitor reduction at both spatial scales tested, indicating that novel species are better competitors, though the relationship is driven mostly by native rather than invasive species. Our results increase our understanding of Darwin’s Naturalization Hypothesis because we are the first to show that novel species are more successful due to increased competitive ability. These results are consistent with many other studies that find a correlation between phylogenetic novelty and spread of invasive species, tapping competition as an important mechanism in invasion.


Tiffany Knight, Department of Biology

Additional Advisors

Erynn Maynard