Diet, adaptation and the evolution of assortative mating in Ceratitis capitata

Nash, William (2015) Diet, adaptation and the evolution of assortative mating in Ceratitis capitata. Doctoral thesis, University of East Anglia.

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The action of natural selection in establishing barriers to gene flow between
populations, or reproductive isolation, is increasingly understood to be a primary driver
of speciation and thus biodiversity. ‘Ecological speciation’ is now supported by evidence
from numerous studies in a range of natural populations. However, experimental tests
of the role of divergent natural selection in the establishment of reproductive isolation
are still scant. To address this omission, the role of larval diet in imposing divergent
selection and causing ecological adaptation and reproductive isolation was tested.
These tests were conducted on the Mediterranean fruit fly (Ceratitis capitata,
Wiedemann) (medfly) model system, which has been relatively under-utilised in the
experimental study of speciation. Using manipulative experiments and experimental
evolution, the three major components of ecological speciation were examined. Firstly
a source of divergent selection was established through quantification of the
consequences of alteration in specific dietary nutrients during the development of
medfly larvae. Following this, similar selective pressures were used as the basis of
experimental evolution of medfly populations reared on divergent developmental diets.
Divergence between these populations was assayed at several time points during
evolution, in real time, using tests for sexual isolation. After 60 generations of
experimental evolution a form of reproductive isolation between populations had
evolved. The mechanism that may have led to the evolution of this isolation was also
explored, through further mating tests, and also the quantification of male courtship
behaviour. The genetic basis of the phenotypes associated with adaptation and sexual
isolation was explored using transcriptomic sequencing and differential expression
analysis of genes expressed in males from the two experimental regimes. A range of
candidate genes was identified as differentially expressed, including genes associated
with oxidative phosphorylation and chemosensation. Taken together, the results of this
research present a novel example of how divergent ecological selection pressure can
lead to the evolution of sexual isolation in experimental populations.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Users 7376 not found.
Date Deposited: 17 Jun 2016 09:12
Last Modified: 30 Sep 2017 00:38


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