Date of Award

12-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science

Committee Member

Dr. Joseph D. Culin, Committee Chair

Committee Member

Dr. William C. Bridges Jr.

Committee Member

Dr. Julia L. Kerrigan

Committee Member

Dr. Geoffrey W. Zehnder

Abstract

The purpose of this study was to determine whether there is a difference in Laricobius nigrinus Fender fecundity between field-collected and laboratory-reared beetles. Laricobius nigrinus used for this study were separated into four cohorts based on origin: Cohort 1 – Wild-caught from Seattle, WA – native population; Cohort 2 – Wild-caught from Banner Elk, NC – naturalized population; Cohort 3 – Laboratory-reared F1generation from Seattle, WA parents; and Cohort 4 – Laboratory-reared F1 generation from Banner Elk, NC parents. In 2013, the first year of this study, gender determination of live beetles had not been developed for L. nigrinus. For that reason, the study was set up following the mass-rearing protocols for L. nigrinus. Due to the scale of the study in 2013, the study yielded only one repetition per cohort. In 2014, new protocols allowed determination of gender of live adults. That allowed me to reduce the scale of the study allowing me to conduct a more detailed replicated study. In 2013, the PNW Cohort yielded fewer live larvae and total (live plus dead) larvae than any other cohort, but produced the highest number of larvae per female. This cohort had a highly skewed male to female ratio with far fewer females compared to males. This is the most likely cause of the low larval production for the PNW Cohort in 2013. In 2014, analyses of the least squares means for the parameters: larvae per female, live larvae, total larvae, and eggs were all significantly greater for field-collected cohorts compared to their respective laboratory-reared F1 offspring. My study confirms that wild-caught cohorts produced a higher number of larvae per female than laboratory-reared cohorts. Variables other than laboratory-rearing, such as L. nigrinus x L. rubidus hybridization and food source differences (i.e., A. tsugae on eastern vs western hemlock), are potential contributors to the observed decrease in larvae per female for wild-caught versus F1cohorts. I recommend further study be conducted on these variables. I also encourage further research into the development of field-insectaries for mass-rearing L. nigrinus.

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