| dc.description.abstract | During meiosis in diploid organisms, Mendel’s laws suggest that homologous
chromosomes should recombine and be randomly distributed to gametes. This is true for meiosis
in most organisms, however, in some cases, chromosome transmission is not random, and can be
biased depending on a number of factors including the parent of origin of a chromosome or
selfish genes located on the chromosome. Why and how non-Mendelian inheritance evolves is
not well understood in many cases, but having a good understanding of the evolution of these
systems is important for establishing under what scenarios non-Mendelian inheritance might
evolve and how meiosis is manipulated by certain chromosomes. This thesis focuses on two
insect clades that exhibit non-Mendelian inheritance: scale insects in the family Eriococcidae and
fungus gnats in the superfamily Sciaroidea. Both of these families exhibit a non-Mendelian
inheritance system known as paternal genome elimination (PGE), where males only transmit
chromosomes inherited from their mother to future generations. In Sciaroidea, I focus on one
species with an unusual genetic system: Bradysia coprophila, which in addition to PGE has an
unusual reproduction system in several other respects. I examine content and evolution of
germline restricted chromosomes, which are present in the germ cells in this species but
eliminated from somatic cells early in development. I characterise how many genes are on these
chromosomes, and explore using genomic methods how these chromosomes evolved. I also
conduct a mating preference experiment on B. coprophila to determine whether the chromosome
inheritance system in this species affects male mating preferences, as this is one case among
animals where we may expect males to evolve mating preferences for certain types of females. In
Eriococcidae, how PGE occurs is labile, and transitions between different types of PGE are not
well understood. I conduct of survey of species to establish how male meiosis differs in species
across this clade, how the type of PGE affects paternal chromosomes in somatic cells, and
whether there is any evidence for transitions to new genetic systems (i.e., loss of PGE) in any
species within this clade. Studying these two insect systems can provide information about what
happens in lineages when non-Mendelian chromosome inheritance evolves. We can determine
how this affects a species behaviour, the mechanisms of chromosome inheritance, and genome
evolution. | en |
