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Convergent Evolution of Darkly Pigmented Skin in Island Melanesian Populations

Bowser, Lauren K
http://orcid.org/0000-0001-8076-7129
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1515508204175712

Abstract Details

2017, MA, University of Cincinnati, Arts and Sciences: Anthropology.
Human skin pigmentation is a highly variable and complex trait that is tightly correlated with the intensity of ultra-violet radiation (UVR). While the evolution of lighter skin pigmentation is fairly well explored, we know far less about the evolution of darker skin color. This thesis uses genetic data to explore two models of pigmentation evolution in Island Melanesia (IM): the Ancestral Variants (AV) and Convergent Evolution (CE) models. The AV model predicts that purifying selection acted to maintain dark skin pigmentation in high UVR regions, and would be supported by observations of low inter-population divergence (measured as FST) at pigmentation loci between populations living in high UVR regions. The CE model predicts that darker skin color has evolved multiple times in human evolutionary history, and would be supported by observations of high FST values at pigmentation loci between populations living in high UVR regions. To address these goals I employed a combination of bioinformatics and wet-laboratory methods. Using allele frequency data from >650,000 single nucleotide polymorphism (SNP) genotypes in the CEPH-HGDP panel I calculated pairwise FST values between IM, African, and East Asian populations. I identified five SNPs (rs2496425, rs3735361, rs1046453, rs3747129, and rs872071) that displayed high divergence between IM and African populations, consistent with predictions of the CE model. In contrast, only two SNPs (rs6979 and rs2234978) displayed significantly high levels of FST between IM and East Asia. 5 SNPs identified in this FST scan were included on a panel of 14 pigmentation-related SNPs genotyped in a sample of 12 IM populations. While some showed little variation, others exhibited high levels of inter-population divergence in IM, suggesting that they may contribute to phenotypic variation. I calculated FST at these loci between IM populations and Yoruban and Han Chinese populations from the 1000 Genomes Project. FST values for IM-Han comparisons were low or moderate for the SNPs rs3782974, rs16982145, rs1800404, and rs1448484, but very great for IM – Yoruban comparisons, consistent with expectations for the CE model. Alternatively the SNPs rs6058017, rs3817362, and rs1800414, showed the opposite pattern, fitting an AV model. Finally, I used pigmentation SNP genotype information from the IM populations and 38 populations from the 1000 Genomes Project to assess global levels of population structure at the 14 pigmentation loci used in this study. My results show that at these 14 loci the 12 IM populations used in this study do not cluster with African populations. This finding does not support predictions of the AV model. Taken together these results indicate that the CE model of darkly pigmented skin in Island Melanesian population is the best fitting model for these SNPs, although not all SNPs fit this pattern. In order to more clearly understand the evolution of darker skin color in Island Melanesian populations it will be necessary to use a larger number of SNPs and to examine a number of different populations across the region.
Heather Norton, Ph.D. (Committee Chair)
C. Jeffrey Jacobson, Ph.D. (Committee Member)
90 p.
Genetics
Molecular Anthropology; Population Genetics; Skin Pigmentation; Island Melanesia; Convergent Evolution

Recommended Citations

Citations

  • Bowser, L. K. (2017). Convergent Evolution of Darkly Pigmented Skin in Island Melanesian Populations [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1515508204175712

    APA Style (7th edition)

  • Bowser, Lauren. Convergent Evolution of Darkly Pigmented Skin in Island Melanesian Populations. 2017. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1515508204175712.

    MLA Style (8th edition)

  • Bowser, Lauren. "Convergent Evolution of Darkly Pigmented Skin in Island Melanesian Populations." Master's thesis, University of Cincinnati, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1515508204175712

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Cincinnati and OhioLINK.