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Title: Inherited parasites in the butterfly Hypolimnas bolina (Lepidoptera: Nymphalidae)
Author: Dyson, Emily Ann
ISNI:       0000 0004 0098 4118
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2002
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Male killing bacteria are known to be widespread in insects, but the factors determining their presence and effects on natural populations are little studied. Studies of the island-inhabiting Hypolimnas bolina were therefore conducted to elucidate the causes and consequences of prevalence variation. Initial investigation of H. bolina in Fiji revealed the presence of a male killing Wolbachia bacterium associated with low egg hatch rates and all-female broods. The prevalence of the male killing Wolbachia is heterogeneous between islands. Sampling in the islands of Independent Samoa indicated the continued presence of highly female-biased populations in this country, associated with the same male killing Wolbachia strain identified from Fiji. The prevalence of the male killer in Independent Samoa is extreme, and this has severe implications on the host population: the lack of males is associated with increased female virginity and decreased female fertility. The effect of infection on female host survival was examined in Fiji: larvae infected with the male killing Wolbachia bacterium show significantly higher survivorship and are significantly heavier as adults indicating a direct benefit to infection. A prevalence survey was carried out using H. bolina samples from eight different countries. Prevalence is heterogeneous across the butterfly's range. Another strain of Wolbachia (that does not kill males) is identified from H. bolina populations in both American Samoa and Fiji. The history of the two different Wolbachia infections was investigated through sequence analysis of the mitochondrial COI genes from butterflies deriving from each of the populations. It is concluded that whilst the male killer has undergone a recent selective sweep, the non male killing Wolbachia strain is ancient. The data also indicated that horizontal transmission of the male killing symbiont must be rare.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available