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Effect of Diet On Symbiont Density Within An Invasive Agricultural Pest

Chang, Alexander (2013)
Master's Thesis (26 pages)
Committee Chair / Thesis Adviser: Gerardo, Nicole Marie
Committee Members: Read, Timothy D ; Real, Leslie
Research Fields: Biology, Ecology; Biology, Entomology
Keywords: Symbiosis; Invasive Species; Context-Dependence; Megacopta cribraria
Program: Laney Graduate School, Biological and Biomedical Sciences (Population Biology, Ecology & Evolution)
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Many insects are host to microbial symbionts that often play a pivotal role in shaping the insects' abilities to utilize resources. Symbioses can be context-dependent, as different biotic and abiotic factors can alter the relationship between symbiont and host. Because of these two factors, the symbionts of invasive insects are important for study as their host ranges can be dictated by their symbionts, and their relationships with their symbionts can be altered by the novel conditions invasive organisms must face. Here, we investigate the relationship between diet and within-host symbiont populations in the stinkbug Megacopta cribraria, which invaded North America in 2009. To examine the host-symbiont association in its new environment, we reared M. cribraria on two alternative host plants, kudzu vines (Pueraria lobata) and soybeans (Glycine max), and measured within-host symbiont densities at various stages of development. We found that juveniles and adult females, but not adult males, reared on soybean had significantly lower symbiont densities than those raised on kudzu. The lowered fitness of the symbiont in insects reared on soybean is surprising as the symbiont is genetically similar to the Japanese strain which confers host usage of soybean; it may be that the soybean in the United States differs from that of Japan. Additionally, the lowered symbiont densities found in adult females reared on soy may impact symbiont transmission, which in turn would limit the potential range for Megacopta cribraria in the United States. These results highlight the impact of environmental context on host-symbiont partnerships.

Table of Contents

Chapter 1: Introduction 1

Symbiosis in Context 1

Study System 2

Figure 1-1 3

Figure 1-2 3

Figure 1-3 5

Chapter 2: Symbiosis of Megacopta cribraria on Alternative host plants 6

Introduction 6

Experimental Procedures 6

Origin of Insects 6

DNA Extraction, Standard Preparation, and qPCR 7

Statistical Analyses 8

Results and Discussion 9

Host Plant Effect on Symbiont Maintenance

Table 2-1 10

Figure 2-1 11

Figure 2-2 12

Figure 2-3 14

Figure 2-4 15

Age and Symbiont Population 16

Conclusion 17

References 18


application/pdf Master's Thesis 26 pages (657.8 KB) [Access copy of Master's Thesis]
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