Thesis

Population Genomics and Phenotypic Variability in Effectiveness of Biological Control in Three Species of Predatory Coccinellids

Predatory coccinellidae are extensively used in biological control of aphids, whiteflies, and other common agricultural pests. Two such species, Coccinella septempunctata and Harmonia axyridis were introduced to the continental United States to bolster this effort and have since been known to become invasive across its current geographical range. Herein we investigate population genomics using ddRADseq technology, here we investigate the genomic diversity, differentiation, and admixture among populations of both C. septempunctata and H. axyridis. Our analyses indicate (1) the presence of population structure, and pervasive inbreeding among our sampled populations of H. axyridis, and (2) extensive gene flow and admixture among all sampled populations of C. septempunctata. Our findings support previous studies that indicate that H. axyridis has not successfully invaded the continental USA, in comparison with C. septempunctata. Additionally, we build a framework for utilizing population genomics as a predictor of the success or failure of augmentative biological control. The convergent lady beetle (Hippodamia convergens) is a generalist natural enemy that is utilized extensively in augmentative biological control across the United States. Recent studies have pointed to both genetic and phenotypic differences in Western (California) versus Eastern (Kansas) populations of the species. Here we investigate phenotypic differences in the utilization of pea aphids in (a) Eastern versus Western populations, (b) Hybrid Eastern and Western populations versus their progenitor populations, and (c) within population interactions in Eastern, Western, and Hybrid populations and developing in conditions of the Western United States. We found no differences between individuals from the Eastern and Western populations nor hybrids of the inbred populations under these conditions in the development of larvae and body mass over their third and fourth instars.

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