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Title: Evolutionary genetics of adaptation in Lepidoptera
Author: Reynolds, Louise
ISNI:       0000 0004 6059 8470
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2016
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Revolutions in sequencing technology have provided an unprecedented opportunity to uncover the genetic basis of traits of adaptive importance, enabling researchers not only to merely describe the means of inheritance of traits but also to establish the genetic changes under selection. This thesis examines the loci involved in two recent episodes of strong selection, namely the suppression of Wolbachia-induced male-killing in the butterfly Hypolimnas bolina and the evolution of melanism in moths. H. bolina has evolved the ability to suppress the male-killing effects of the heritable endosymbiont Wolbachia. This thesis demonstrates firstly that this results from a single locus trait that doesn't involve genetic variants beyond chromosome 25. This simple genetic basis explains in part the speed of spread of the suppressor in natural populations. The hypothesis that the insect sex determination gene doublesex is the target of selection is then examined. Compatible with this hypothesis, doublesex variants were found to cosegregate with suppression, and that the peak of a selective sweep is located within doublesex region. An unusual pattern of inheritance was uncovered at the doublesex locus, suggestive of a duplication event. These data are consistent with, though not proof of, Wolbachia driving the evolution of this key sex determination gene. The progression of a selective sweep for the suppression, as it travelled in space across Independent Samoa, was then examined. The sweep across Independent Samoa corroborated the genomic region immediately around doublesex as the target of selection. The sweep was very broad but weakened as it progressed across Samoa. The thesis then examines the genetic basis of melanism in Lepidoptera, and compares the genomic region associated with a naturally selected melanistic form to a laboratory mutant. The 'natural' example corresponded to a known genomic hotspot for colour pattern evolution, whereas this region was excluded in the laboratory mutants. These data support the pleiotropic view of convergence - that involvement of a single region is associated with minimized non-target effects. The thesis ends with a discussion of these data and a programme for future research in the area.
Supervisor: Hurst, G. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral