Classical weed biological control uses natural enemies that have co-evolved with their host plants in their native range and provides a sustainable and effective strategy for the long-term management of invasive species. However, its successful implementation encounters several challenges that must be addressed to maximize efficacy. Biological control agents, often reared extensively in quarantine, face issues like adaptation to culture, reduced genetic diversity and inbreeding, which can affect their establishment and efficacy. Upon implementation of biological control, site restoration may be limited without the proper integration of supplemental restoration techniques. Restoration techniques combined with biological control are not extensively studied, limiting their widespread adoption and application. Furthermore, the impact of invasive species to native species of concern is important to optimize management plans. This dissertation investigates the integration of applied and evolutionary approaches in the control of invasive swallow-wort vines (Vincetoxicum spp.), emphasizing the importance of genetic background when employing the biocontrol agent Hypena opulenta, the restoration of invaded forests, and the implications for the monarch butterfly (Danaus plexippus). In Chapter 1, I research the importance of genetic background by creating an outbred population by crossing a long-term laboratory-reared population with individuals from an-established population of H. opulenta in the field. These populations are used to understand the role of intraspecific outcrossing in enhancing the fitness and neutral genetic diversity of Hypena opulenta with laboratory and field experiments alongside molecular analysis. The results show that increases in neutral genetic variation can translate to tangible fitness benefits in the outbred population measured as increases in production of pupae in the laboratory, and larval feeding rates and second-generation adult production under field conditions. In Chapter 2, I research how biological control, manual removal of swallow-wort, and native seeding, alone and combined, can impact restoration success. The results show that when native seeding is combined with biological control, swallow-wort cover is reduced, and species richness is enhanced. In Chapter 3, I investigate the effects of genetic background and demography in the establishment success of Hypena opulenta by conducting experimental field releases. However, I was not able to understand this relationship because of establishment failure. In repeat releases two years later, where genetic background was the sole focus, the results mirrored patterns seen in the field cage experiments from Chapter 1 with the outbred population eating more plant tissue and producing more adults compared to lower genetic diversity laboratory reared and field collected populations. Finally, in Chapter 4, I explore the oviposition choices of the monarch butterfly in Michigan. I determine the frequency with which monarch butterflies mistakenly lay eggs on swallow-worts under natural field conditions and use laboratory experiments to uncover the underlying mechanisms of their oviposition decisions, aiming to clarify the factors influencing monarch egg-laying behavior. Field results showed that monarchs can lay up to 17% of their eggs on swallow-wort locally, and about 8% overall. Despite oviposition failure in the lab experiment, monarch larvae exhibited 16% mortality in the lab directly attributed to feeding on swallow-wort. This dissertation contributes to the discourse on ecological restoration, biological control, and provides insights for future conservation and management endeavors in ecosystems threatened by invasive species.
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