Date of Award


Document Type

Honors Thesis (Colby Access Only)


Colby College. Biology Dept.


Judy Stone


Biological invasions are a global concern due to their devastating biological and financial consequences. Although the field of invasion biology has increased considerably, there is still much to be learned about the genetic, environmental, and anthropogenic factors that influence a species’ ability to exhibit invasive behavior. Several studies suggest that invasive behavior can arise from hybrid vigor as a result of interspecific hybridization; however, not much work has been done on the effects of intraspecific hybridization in causing invasive behavior. For intraspecific hybridization to be possible, it is likely that multiple introductions of the same species to a novel environment are necessary to provide disparate genotypes. In this study, I used pin oak (Quercus palustris), a tree native to the Midwest but planted ornamentally throughout the United States, as a model to study multiple introductions as a facilitator of intraspecific hybridization and a trigger for invasive behavior in a novel environment. Planted and wild pin oaks on Colby College’s campus in Waterville, Maine were genotyped at three chloroplast (maternally-inherited) and ten nuclear (biparentally-inherited) loci using simple sequence repeat (SSR) markers. Based on the nuclear SSR data, inbreeding coefficients of the parental and F1 generations were calculated using GenAlEx. The results indicated that both generations were equally inbred. Furthermore, most wild pin oaks were found to have been produced by genetically similar parents from the same introduction. As a result, I concluded that for the pin oaks on Colby’s campus, hybrid vigor is not the cause of invasive behavior. Further studies could test if release from enemies could have triggered invasive behavior in Colby’s pin oaks. Additionally, other invasive pin oak populations could be tested for hybrid vigor.


Biological invasion, population genetics, pin oak, Quercus palustris, multiple introductions