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|Hartfield2012_redact.pdf||Signature removed||4.79 MB||Adobe PDF||View/Open||Chapter4.nb||Data||3.75 MB||Unknown||Chapter6.nb||Data||341.38 kB||Unknown||Hartfield2012.pdf||Full thesis||4.86 MB||Adobe PDF|
|Title: ||Evolution of sex and recombination in large, finite populations|
|Authors: ||Hartfield, Matthew|
|Supervisor(s): ||Keightley, Peter|
|Issue Date: ||22-Jun-2012|
|Publisher: ||The University of Edinburgh|
|Abstract: ||This thesis investigates how breaking apart selection interference (‘Hill-Robertson’ effects)
that arises between linked loci can select for higher levels of recombination.
Specifically, it mainly studies how the presence of both advantageous and deleterious
mutation affects selection for recombination. These evolutionary advantages are subsequently
investigated with regards to sex resisting asexual invasion in a subdivided
i) KEIGHTLEY and OTTO (2006) showed a strong advantage to recombination in
breaking apart selection interference, if it acts across multiple, linked loci subject to
recurrent deleterious mutation. Their model is modified to consider selection acting
on recombination if a small proportion of mutations are advantageous. This leads
to a greater increase in selection acting on a recombination modifier, compared to
cases where only deleterious mutations are present.
ii) Branching-process methods are developed to quantify how likely it is that a deleterious
mutant hitchhikes with a selective sweep, and how recombination between
the two loci affects this process. This is compared to the neutral hitchhiking model,
to determine how levels of linked neutral diversity would differ between the two
scenarios. A simple application with regards to human genetic data is provided.
iii) Population subdivision can maintain costly sex, as a consequence of restricted gene
flow slowing the spread of invading asexuals, which leads to an excessive accumulation
of deleterious alleles. However, previous work did not quantify whether
costly sex can be maintained with realistic levels of population subdivision. Simulations
in this thesis show that the level of population subdivision (as measured by
Fst) needed to maintain costly sex decreases with larger population size; however
critical Fst values found are generally high, compared to surveys of geographicallyclose
populations. The lowest levels of population subdivision that maintained sex
were found if mutation is both advantageous and deleterious, and demes were arranged
in a one-dimensional stepping-stone formation.
iv) An analytical method is developed to calculate how long it takes an advantageous
mutation (such as an invading asexual) to spread through a subdivided population.
The flexibility of the methods created means that they can be applied to different
types of stepping-stone populations. It is shown how to formulate the fixation
time for one-dimensional and two-dimensional structures, with analytical methods
showing a good fit to simulation data.|
|Sponsor(s): ||Biotechnology and Biological Sciences Research Council (BBSRC)|
|Keywords: ||Multilocus simulations|
|Appears in Collections:||Biological Sciences thesis and dissertation collection|
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