Generally, sexual organisms contain two haploid genomes, one from each parent, united in a single diploid nucleus of the zygote which links their fate during growth. A fascinating exception to this are Basidiomycete fungi, where the two haploid genomes remain separate in a dikaryon, retaining the option to fertilize subsequent monokaryons encountered. How the ensuing nuclear competition influences the balance of selection within and between individuals is largely unexplored. We test the consequences of the dikaryotic lifecycle for mating success and mycelium-level fitness components. We assume a tradeoff between mating fitness at the level of the haploid nucleus and fitness of the fungal mycelium. We show that the maintenance of fertilization potential by dikaryons leads to a higher proportion of fertilized monokaryons, but that the ensuing intra-dikaryon selection for increased nuclear mating fitness leads to reduced mycelium fitness relative to a diploid life cycle. However, this fitness reduction is lower compared to a hypothetical life cycle where dikaryons can also exchange nuclei. Prohibition of fusion between dikaryons therefore reduces the level of nuclear parasitism. The number of loci influencing fitness is an important determinant of the degree to which average mycelium-level fitness is reduced. The results of this study crucially hinge upon a tradeoff between nucleus and mycelium-level fitness. We discuss the evidence for this assumption and the implications of an alternative that there is a positive relationship between nucleus and mycelium-level fitness.

中文翻译：

---

共同生活：模拟蘑菇形成真菌双核生命周期对基因组冲突的影响

通常，有性生物包含两个单倍体基因组，每个亲本一个，结合在受精卵的单个二倍体核中，这将它们在生长过程中的命运联系起来。一个有趣的例外是担子菌属真菌，其中两个单倍体基因组在双核中保持分离，保留了使后续遇到的单核体受精的选择。随之而来的核竞争如何影响个体内部和个体之间的选择平衡在很大程度上尚未得到探索。我们测试了双核生命周期对交配成功和菌丝体水平健康成分的影响。我们假设在单倍体核水平的交配适应性和真菌菌丝体的适应性之间进行权衡。我们表明，双核子维持受精潜力会导致受精单核子的比例更高，但是随后的双核内选择以增加核交配适应性导致相对于二倍体生命周期的菌丝体适应性降低。然而，与双核子也可以交换核的假设生命周期相比，这种适应度降低要低。因此，禁止双核之间的融合会降低核寄生水平。影响适应度的基因座数量是平均菌丝体水平适应度降低程度的重要决定因素。这项研究的结果关键取决于细胞核和菌丝体水平适应性之间的权衡。我们讨论了这一假设的证据以及细胞核和菌丝体水平适应性之间存在正相关关系的替代方案的含义。