Department of Integrative Biology, University of California-Berkeley, 3060 Valley Life Sciences Building, Berkeley, California, 94720-3140, USA.
Evolution. 2011 Sep;65(9):2706-11. doi: 10.1111/j.1558-5646.2011.01322.x. Epub 2011 May 10.
Genomes vary greatly in size and complexity, and identifying the evolutionary forces that have generated this variation remains a major goal in biology. A controversial proposal is that most changes in genome size are initially deleterious and therefore are linked to episodes of decrease in effective population sizes. Support for this hypothesis comes from large-scale comparative analyses, but vanishes when phylogenetic nonindependence is taken into account. Another approach to test this hypothesis involves analyzing sequence evolution among clades where duplications have recently fixed. Here we show that episodes of fixation of duplications in mitochondrial genomes of the gecko Heteronotia binoei (two independent clades) and of mantellid frogs (five distinct branches) coincide with reductions in the ability of selection to purge slightly deleterious mutations. Our results support the idea that genome complexity can arise through nonadaptive processes in tetrapods.
基因组在大小和复杂性上存在很大差异，确定导致这种变异的进化力量仍然是生物学的主要目标。一个有争议的观点是，大多数基因组大小的变化最初是有害的，因此与有效种群大小减少的时期有关。这一假说得到了大规模比较分析的支持，但当考虑到系统发育非独立性时，这种支持就消失了。另一种检验这一假说的方法是分析最近固定在重复分支中的进化枝之间的序列进化。在这里，我们表明，壁虎 Heteronotia binoei（两个独立的分支）和 Mantellid 青蛙（五个不同的分支）线粒体基因组中重复固定的时期与选择清除轻微有害突变的能力降低相一致。我们的结果支持了基因组复杂性可以通过四足动物的非适应性过程产生的观点。
