Influence of the mutation load on the genomic composition of hybrids between outcrossing and self-fertilizing species.

Hybridization is a natural process whereby two diverging evolutionary lineages reproduce and create offspring of mixed ancestry. Differences in mating systems (e.g., self‐fertilization and outcrossing) are expected to affect the direction and extent of hybridization and introgression in hybrid zones. Among other factors, selfers and outcrossers are expected to differ in their mutation loads. This has been studied both theoretically and empirically; however, conflicting predictions have been made on the effects mutation loads of parental species with different mating systems can have on the genomic composition of hybrids. Here, we develop a multi‐locus, selective model to study how the different mutation load built up in selfers and outcrossers as a result of selective interference and homozygosity impact the long‐term genetic composition of hybrid populations. Notably, our results emphasize that genes from the parental population with lesser mutation load get rapidly overrepresented in hybrid genomes, regardless of the hybrids own mating system. When recombination tends to be more important than mutation, outcrossers' genomes tend to be of higher quality and prevail. When recombination rates are low, however, selfers' genomes may reach higher quality than outcrossers' genomes and prevail in the hybrids. Taken together, these results provide concrete insights into one of the multiple factors influencing hybrid genome ancestry and introgression patterns in hybrid zones containing species with different mating systems. Genomic composition of hybrids between species with different mating systems (selfers and outcrossers) can be influenced by many parameters, including recombination rates, mutation rates, and hybrid mating systems. Here, we show that genes from the parental species with least mutation load tend to prevail, and that hybrid's own mating system appears to have only a limited influence on hybrid ancestry.

杂交是一个自然过程，在此过程中两个分化的进化谱系进行繁殖并产生混血后代。交配系统的差异（例如自交和异交）预计会影响杂交区域内杂交和基因渗入的方向及程度。在其他因素中，自交者和异交者的突变负荷预计会有所不同。这已经在理论和实证方面都进行了研究；然而，对于具有不同交配系统的亲本物种的突变负荷对杂交种基因组组成的影响，已经做出了相互矛盾的预测。在此，我们建立了一个多位点的选择模型，以研究由于选择干扰和纯合性，自交者和异交者中积累的不同突变负荷如何影响杂交种群的长期遗传组成。值得注意的是，我们的结果强调，无论杂交种自身的交配系统如何，来自突变负荷较小的亲本种群的基因在杂交基因组中会迅速过度表达。当重组往往比突变更重要时，异交者的基因组往往质量更高并占优势。然而，当重组率较低时，自交者的基因组可能比异交者的基因组质量更高，并在杂交种中占优势。综上所述，这些结果为影响包含具有不同交配系统的物种的杂交区域内杂交基因组血统和基因渗入模式的众多因素之一提供了具体的见解。 具有不同交配系统（自交者和异交者）的物种之间杂交种的基因组组成可能受到许多参数的影响，包括重组率、突变率和杂交交配系统。在此，我们表明来自突变负荷最小的亲本物种的基因往往占优势，并且杂交种自身的交配系统似乎对杂交血统只有有限的影响。