Andolfatto P
Institute of Cell, Animal and Population Biology, University of Edinburgh, Edinburgh, Scotland.
Mol Biol Evol. 2001 Mar;18(3):279-90. doi: 10.1093/oxfordjournals.molbev.a003804.
Surveys of molecular variation in Drosophila melanogaster and Drosophila simulans have suggested that diversity outside of Africa is a subset of that within Africa. It has been argued that reduced levels of diversity in non-African populations reflect a population bottleneck, adaptation to temperate climates, or both. Here, I summarize the available single-nucleotide polymorphism data for both species. A simple "out of Africa" bottleneck scenario is consistent with geographic patterns for loci on the X chromosome but not with loci on the autosomes. Interestingly, there is a trend toward lower nucleotide diversity on the X chromosome relative to autosomes in non-African populations of D. melanogaster, but the opposite trend is seen in African populations. In African populations, autosomal inversion polymorphisms in D. melanogaster may contribute to reduced autosome diversity relative to the X chromosome. To elucidate the role that selection might play in shaping patterns of variability, I present a summary of within- and between-species patterns of synonymous and replacement variation in both species. Overall, D. melanogaster autosomes harbor an excess of amino acid replacement polymorphisms relative to D. simulans. Interestingly, range expansion from Africa appears to have had little effect on synonymous-to-replacement polymorphism ratios.
对黑腹果蝇和拟暗果蝇分子变异的调查表明，非洲以外地区的多样性是非洲内部多样性的一个子集。有人认为，非洲以外种群中多样性水平的降低反映了种群瓶颈、对温带气候的适应，或两者兼而有之。在这里，我总结了这两个物种现有的单核苷酸多态性数据。一个简单的“走出非洲”瓶颈情景与X染色体上基因座的地理模式一致，但与常染色体上的基因座不一致。有趣的是，在黑腹果蝇的非洲以外种群中，相对于常染色体，X染色体上的核苷酸多样性有降低的趋势，但在非洲种群中则呈现相反的趋势。在非洲种群中，黑腹果蝇的常染色体倒位多态性可能导致相对于X染色体常染色体多样性降低。为了阐明选择在塑造变异模式中可能发挥的作用，我总结了这两个物种种内和种间同义变异和替换变异的模式。总体而言，相对于拟暗果蝇，黑腹果蝇的常染色体含有过多的氨基酸替换多态性。有趣的是，从非洲的范围扩张似乎对同义替换多态性比率几乎没有影响。
