Instituto Gulbenkian de Ciência, Oeiras, Portugal.
Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI, USA.
Evolution. 2023 Oct 3;77(10):2162-2172. doi: 10.1093/evolut/qpad125.
Hybridization opens a unique window for observing speciation mechanisms and is a potential engine of speciation. One controversially discussed outcome of hybridization is homoploid hybrid speciation by reciprocal sorting, where a hybrid population maintains a mixed combination of the parental genetic incompatibilities, preventing further gene exchange between the newly formed population and the two parental sources. Previous work showed that, for specific linkage architectures (i.e., the genomic location and order of hybrid incompatibilities), reciprocal sorting could reliably result in hybrid speciation. Yet, the sorting of incompatibilities creates a risk of population extinction. To understand how the demographic consequences of the purging of incompatibilities interact with the formation of a hybrid species, we model an isolated hybrid population resulting from a single admixture event. We study how population size, linkage architecture, and the strength of the incompatibility affect survival of the hybrid population, resolution/purging of the genetic incompatibilities and the probability of observing hybrid speciation. We demonstrate that the extinction risk is highest for intermediately strong hybrid incompatibilities. In addition, the linkage architecture displaying the highest hybrid speciation probabilities changes drastically with population size. Overall, this indicates that population dynamics can strongly affect the outcome of hybridization and the hybrid speciation probability.
杂交为观察物种形成机制提供了一个独特的窗口，是物种形成的潜在动力。杂交的一个有争议的结果是同倍体杂种通过相互排序形成物种，其中杂种群体保持了亲本遗传不相容性的混合组合，阻止了新形成的群体与两个亲本来源之间的进一步基因交换。先前的工作表明，对于特定的连锁结构（即杂种不相容性的基因组位置和顺序），相互排序可以可靠地导致杂种形成物种。然而，不相容性的排序会带来种群灭绝的风险。为了了解不相容性消除的人口统计学后果如何与杂种物种的形成相互作用，我们对来自单一混合事件的隔离杂种群体进行建模。我们研究了种群大小、连锁结构和不相容性的强度如何影响杂种群体的生存、遗传不相容性的解决/消除以及观察杂种形成物种的概率。我们证明，对于中等强度的杂种不相容性，灭绝风险最高。此外，显示最高杂种形成概率的连锁结构随种群大小而急剧变化。总体而言，这表明种群动态可以强烈影响杂交的结果和杂种形成的概率。
