Horizontal gene transfer (HGT), or lateral gene transfer, is the non-sexual movement of genetic information between genomes. It has played a pronounced part in bacterial and archaeal evolution, but its role in eukaryotes is less clear. Behaviours unique to eukaryotic cells — phagocytosis and endosymbiosis — have been proposed to increase the frequency of HGT, but nuclear genomes encode fewer HGTs than bacteria and archaea. Here, I review the existing theory in the context of the growing body of data on HGT in eukaryotes, which suggests that any increased chance of acquiring new genes through phagocytosis and endosymbiosis is offset by a reduced need for these genes in eukaryotes, because selection in most eukaryotes operates on variation not readily generated by HGT.

水平基因转移（HGT）或横向基因转移是基因组之间遗传信息的非性移动。它在细菌和古菌进化中发挥了重要作用，但它在真核生物中的作用尚不清楚。真核细胞特有的行为——吞噬作用和内共生——被认为可以增加 HGT 的频率，但核基因组编码的 HGT 少于细菌和古细菌。在这里，我在真核生物中 HGT 数据不断增长的背景下回顾了现有的理论，这表明通过吞噬作用和内共生获得新基因的任何增加的机会都会被真核生物中对这些基因的需求减少所抵消，因为选择大多数真核生物依靠 HGT 不易产生的变异进行运作。