“Fly around & find out” - An anthology of selection experiments on sexual conflict and speciation in Drosophila melanogaster.
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Authors
Thyagarajan, Harshavardhan
Date
2024-07-03
Type
thesis
Language
eng
Keyword
Evolution , Biology , Sexual Conflict , Speciation , Genetics
Alternative Title
Abstract
Sexual conflict is a catchment area, collecting all forms of fitness costs spilling over from disharmony between the sexes of a species. In chapter 1, I introduce the forms of sexual conflict, and chart a history of the field by reviewing selection experiments used to study this conflict through manipulations of mating systems, reproductive outcomes, and genetic inheritance patterns. In addition to synthesizing this discipline, I present open questions as identified by theory, and under-studied but ecologically and taxonomically valuable research
directions.
The genetic material of the sexes is shared but undergoes divergent selection pressures. Amongst other outcomes, this is expected to contribute to the maintenance of heritable trait polymorphisms. The existence and genomic coordinates of these sexually antagonistic (SA) polymorphisms represent important open questions in evolutionary biology. Chapter 2 describes a selection experiment designed to address these questions.
Divergent selection on the sexes is artificially replaced with directional (male-limited “ML”) selection, which is expected to result in male-benefit adaptive changes and a reduction of heritable variance at SA loci. Replicating test conditions used in previous ML experiments, I find evidence for improved male fitness at the cost of female fitness and critically, a reduction of genetic variance for male fitness. However, I use an improved breeding design to demonstrate that these benefits are not general, suggesting that the selection design includes
alternative sources of selection that obscure our ability to characterize SA loci and variance.
Chapter 3 addresses this concern, identifies sources of alternative selection, and levels a critique of this system of experimentation as it has been used. I demonstrate adaptive responses to a nuclear-cytoplasmic mismatch (due to male-harming cytoplasmic genes under matrilinear inheritance), a shared Y chromosome (as against the usual patrilinear Y) and arrested male-female coevolution.
In chapter 4, I deviate from the central theme established thus far to study speciation. Populations with restricted gene flow and varied selection pressures are expected to undergo reproductive isolation (RI) over evolutionary timescales. Using a long-term evolution experiment (LTEE) with divergent life-history selection between allopatric populations, I demonstrate the evolution of bi-directional premating RI through female mate choice tempered by asymmetric mating rate conflict in the populations.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution 4.0 International