Evolutionary forces shaping innate immune gene variation in a bottlenecked population of the Seychelles warbler

Gilroy, Danielle (2015) Evolutionary forces shaping innate immune gene variation in a bottlenecked population of the Seychelles warbler. Doctoral thesis, University of East Anglia.

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In this thesis, I investigated different evolutionary forces in shaping genetic variation within
a bottlenecked population of an island species, the Seychelles warbler (Acrocephalus
sechellensis). I specifically explore pathogen-mediated selection within this system by using
avian beta-defensins and toll-like receptor genes to examine functional variation. First, I
characterise variation within both gene groups in this population and show that this species’
demographic history has had an overriding effect on selection and random drift is the
predominant evolutionary force. I characterise variation within these gene groups across
several other Acrocephalus species, in addition to looking at a specific locus in a prebottlenecked
population in order to directly compare genetic variation pre- and postbottleneck.
I use population genetic statistical methods to detect selection at several
polymorphic genes and evaluate the robustness of these methods when applied to singlelocus
sequence data, which may be lacking in power and not meet the demographic
assumptions that come with these tests. To overcome this, I designed forward-in-time
simulations based on microsatellite markers used in pre- and post-bottleneck populations of
the Seychelles warbler. I am able to delineate the evolutionary effects of selection from drift
and show that some toll-like receptor genes are indeed under positive balancing selection in
spite of the recent bottleneck. I further explore how this variation is maintained by
conducting association analyses investigating innate immune gene variation and its
relationship with individual survival and malarial susceptibility / resistance. Environmental
factors are also considered. By investigating the consequences of functional variation in a
bottlenecked species we are able to assess its long-term viability and adaptive potential,
whilst elucidating the evolutionary importance of maintaining genetic variation in natural

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Users 2259 not found.
Date Deposited: 04 May 2016 08:55
Last Modified: 04 May 2016 08:55
URI: https://ueaeprints.uea.ac.uk/id/eprint/58552

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