Department of Ecology and Evolutionary Biology, Rice University, 6100 Main St., Houston, Texas 77005, USA.
Evolution. 2010 Jul;64(7):2097-109. doi: 10.1111/j.1558-5646.2010.00967.x. Epub 2010 Feb 9.
Genome sizes vary widely among species, but comprehensive explanations for the emergence of this variation have not been validated. Lynch and Conery (2003) hypothesized that genome expansion is maladaptive, and that lineages with small effective population size (N(e)) evolve larger genomes than those with large N(e) as a consequence of the lowered efficacy of natural selection in small populations. In addition, mating systems likely affect genome size evolution via effects on both N(e) and the spread of transposable elements (TEs). We present a comparative analysis of the effects of N(e) and mating system on genome size evolution in seed plants. The dataset includes 205 species with monoploid genome size estimates (corrected for recent polyploidy) ranging from 2Cx = 0.3 to 65.9 pg. The raw data exhibited a strong positive relationship between outcrossing and genome size, a negative relationship between N(e) and genome size, but no detectable N(e)x outcrossing interaction. In contrast, phylogenetically independent contrast analyses found only a weak relationship between outcrossing and genome size and no relationship between N(e) and genome size. Thus, seed plants do not support the Lynch and Conery mechanism of genome size evolution. Further work is needed to disentangle contrasting effects of mating systems on the efficacy of selection and TE transmission.
物种之间的基因组大小差异很大，但对于这种变异的出现，还没有得到全面的解释。林奇和科纳里（2003 年）假设，基因组的扩张是不利的，具有小有效种群大小（Ne）的谱系比具有大 Ne 的谱系更容易进化出更大的基因组，这是由于小种群中自然选择的效率降低所致。此外，交配系统可能通过对 Ne 和转座元件（TEs）的传播的影响来影响基因组大小的进化。我们对种子植物中 Ne 和交配系统对基因组大小进化的影响进行了比较分析。该数据集包括 205 个物种，其单倍体基因组大小估计值（纠正了最近的多倍体）范围为 2Cx = 0.3 至 65.9 pg。原始数据显示，异交与基因组大小之间存在很强的正相关关系，Ne 与基因组大小之间存在负相关关系，但未检测到 Nex 异交相互作用。相比之下，系统发育独立对比分析发现，异交与基因组大小之间只有微弱的关系，Ne 与基因组大小之间没有关系。因此，种子植物并不支持林奇和科纳里的基因组大小进化机制。需要进一步的工作来理清交配系统对选择和 TE 传播效率的对比影响。
