Mitochondrial heteroplasmy in an emerging insect pest and its implications for understanding invasion histor

Animal mitochondria have long been considered to be primarily maternally inherited, however in recent years as molecular techniques have become more cost effective and the ability to discriminate minor allele variants more powerful examples of heteroplasmy---the presence of more than one mitochondrial lineage within a cell/organism---have come to light. The mechanisms by which heteroplasmy may be induced are multiple, depending upon how the alternative haplotype is introduced; whether through mutation or paternal inheritance. In this thesis it is shown that heteroplasmy occurs in the bed bug, Cimex lectularius, at very high rates relative to other species where it has been noted. Bed bugs were collected from the South Central United States and screened for signs of mitochondrial heteroplasmy. To distinguish the potential mechanisms and prevalence of heteroplasmy the identities of the constituent haplotypes were determined through sub-cloning. There appeared to be no bias in frequency of heteroplasmy due to age, or sex. Extermination attempts resulted in a lower frequency of heteroplasmy in a population. Given the identity of the recovered haplotypes it is not likely that the alternate forms are the result of nuclear integration of mitochondrial DNA (mtDNA). There was no correlation between phylogenetic distance and geographic distance in these recovered haplotypes and heteroplasmy did not appear geographically structured. The haplotypes recovered suggest that heteroplasmy in the bed bug is driven by the leakage and persistence of sperm mitochondria into the egg, termed paternal leakage. It was not possible within the scope of this study to determine whether paternal leakage resulted from a breakdown of oocytotic mechanisms of elimination or concerted evolution of avoidance in the sperm mitochondria. The high frequency of heteroplasmy could serve to contribute additional genetic diversity to the often-inbred infestations characteristic of this species.;Dispersal of human associated pests can have unique spatial tendencies. Molecular markers can reveal much about propagules and the populations they originated in. These inferences are based upon assumptions of the marker's inheritance and diversity. Occasionally molecular markers will show vastly different patterns of population history. The co-inheritance of maternal and paternal mitochondria could have significant impacts on the inferences made with these markers. To assess the influence of heteroplasmy in generating contradicting patterns from mitochondrial and nuclear markers a case study was performed. While nuclear markers support a single invasion of, mtDNA infers a genetically diverse origin resulting from either multiple invasions of independent origin, or the introduction of a founding propagule with multiple mitochondrial variants. Heteroplasmy can thus result in a mtDNA diverse introduction, but is not sufficient in explaining the level of diversity observed. I therefore propose mtDNA recombination as a possible mechanism for in situ diversification.