Drift, not selection, shapes toll-like receptor variation among oceanic island populations

Gonzalez-Quevedo, Catalina, Spurgin, Lewis G, Illera, Juan Carlos and Richardson, David S (2015) Drift, not selection, shapes toll-like receptor variation among oceanic island populations. Molecular Ecology, 24 (23). pp. 5852-5863. ISSN 0962-1083

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    Abstract

    Understanding the relative role of different evolutionary forces in shaping the level and distribution of functional genetic diversity among natural populations is a key issue in evolutionary and conservation biology. To do so accurately genetic data must be analyzed in conjunction with an unambiguous understanding of the historical processes that have acted upon the populations. Here we focused on diversity at toll-like receptor (TLR) loci, which play a key role in the vertebrate innate immune system and, therefore, are expected to be under pathogen-mediated selection. We assessed TLR variation within and among 13 island populations (grouped into three archipelagos) of Berthelot's pipit, Anthus berthelotii, for which detailed population history has previously been ascertained. We also compared the variation observed with that found in its widespread sister species, the tawny pipit, Anthus campestris. We found strong evidence for positive selection at specific codons in TLR1LA, TLR3 and TLR4. Despite this, we found that at the allele frequency level, demographic history has played the major role in shaping patterns of TLR variation in Berthelot's pipit. Levels of diversity and differentiation within and across archipelagos at all TLR loci corresponded very closely with neutral microsatellite variation, and with the severity of the bottlenecks that occurred during colonization. Our study shows that despite the importance of TLRs in combating pathogens, demography can be the main driver of immune gene variation within and across populations, resulting in patterns of functional variation that can persist over evolutionary timescales. This article is protected by copyright. All rights reserved.

    Item Type: Article
    Additional Information: This is an open access article under the terms of the Creative Commons Attribution License,which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
    Uncontrolled Keywords: anthus berthelotii,berthelot’s pipit,bottleneck,genetic drift,selection,toll-like receptors,founder effects,genetic variation
    Faculty \ School: Faculty of Science > School of Biological Sciences
    Depositing User: Pure Connector
    Date Deposited: 01 Dec 2015 07:30
    Last Modified: 03 Apr 2019 01:02
    URI: https://ueaeprints.uea.ac.uk/id/eprint/55541
    DOI: 10.1111/mec.13437

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