Stephan W, Li H
Section of Evolutionary Biology, Department of Biology II, University of Munich, Planegg-Martinsried, Germany.
Heredity (Edinb). 2007 Feb;98(2):65-8. doi: 10.1038/sj.hdy.6800901. Epub 2006 Sep 27.
Population genetic analyses of the past two decades confirmed an earlier hypothesis by L Tsacas and D Lachaise that the cosmopolitan species Drosophila melanogaster has an Afrotropical origin, and that it colonized the rest of the world only very recently. Maximum likelihood analyses based on multilocus data suggest that the putative ancestral African population expanded its size about 60,000 years ago (ya). These demographic changes were accompanied by the fixation of numerous beneficial mutations, as revealed by signatures of positive directional selection in the genome (selective sweeps). The estimated rate of adaptive substitution on the X chromosome is in the order of 10(-11) per nucleotide site per generation. Comparable (but not significantly higher) substitution rates are found in derived populations that colonized new habitats outside Africa, such as in a European population that branched off from the African lineage about 16,000 ya.
过去二十年的群体遗传学分析证实了L·察卡斯和D·拉沙伊早期提出的一个假说，即世界性物种黑腹果蝇起源于非洲热带地区，并且直到最近才扩散到世界其他地区。基于多位点数据的最大似然分析表明，假定的非洲祖先种群在约6万年前（ya）扩大了规模。正如基因组中正向选择的特征（选择性清除）所揭示的那样，这些人口统计学变化伴随着大量有益突变的固定。估计X染色体上适应性替代的速率约为每代每个核苷酸位点10^(-11)。在殖民非洲以外新栖息地的衍生种群中也发现了相当（但并非显著更高）的替代率，例如在约1.6万年前从非洲谱系分支出来的一个欧洲种群中。
