Mating systems have profound effects on genetic diversity and compatibility. The convergent evolution of self-fertilization in three Caenorhabditis species provides a powerful lens to examine causes and consequences of mating system transitions. Among the selfers, C. tropicalis is the least genetically diverse and most afflicted by outbreeding depression. We generated a chromosomal-scale genome for C. tropicalis and surveyed global diversity. Population structure is very strong, and islands of extreme divergence punctuate a genomic background that is highly homogeneous around the globe. Outbreeding depression in the laboratory is caused largely by multiple gene drive elements, genetically consistent with maternal toxin/zygotic antidote systems. Driver loci harbor novel and duplicated genes, and their activity is modified by mito-nuclear background. Segregating drivers dramatically reduce fitness, and simulations show that selfing limits their spread. Frequent selfing in C. tropicalis may therefore be a strategy to avoid drive-mediated outbreeding depression.

中文翻译：

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自交是热带念珠菌最安全的性行为

交配系统对遗传多样性和兼容性具有深远的影响。三种秀丽隐杆线虫的自我受精趋同进化为检查交配系统过渡的原因和后果提供了有力的证明。在这些自交者中，热带衣原体的遗传多样性最少，受近亲抑郁症的影响最大。我们生成了热带假丝酵母的染色体规模基因组并调查了全球多样性。人口结构非常强大，极端分歧的岛屿标志着全球高度同质的基因组背景。实验室中的近亲繁殖衰退主要是由多种基因驱动因素引起的，这些基因驱动因素在遗传上与母体毒素/合子解毒剂系统一致。驱动基因座包含新的和重复的基因，其活性被线粒体-核背景修饰。隔离驱动程序会大大降低适应性，并且仿真显示，自私限制了其传播。因此，热带假丝酵母的频繁自交可能是避免驱动介导的近交衰退的策略。