Data from: Parapatric speciation in three islands: dynamics of geographic configuration of allele sharing

We studied the time to speciation by geographic isolation for a species living on three islands connected by rare migration. We assumed that incompatibility was controlled by a number of quantitative loci and that individuals differing in loci by more than a threshold did not mix genetically with each other. For each locus, we defined the geographic configuration (GC), which specifies islands with common alleles, and traced the stochastic transitions between different GCs. From these results, we calculated the changes in genetic distances. Since a single migration event provides an opportunity for transitions in multiple loci, the GCs of different loci are correlated, which can be evaluated by constructing the stochastic differential equations of the number of loci with different GCs. Our model showed that the low number of incompatibility loci facilitates parapatric speciation and that migrants arriving as a group shorten the waiting time to speciation compared to the same number of migrants arriving individually. We also discuss how speciation rate changes with geographic structure.

我们针对栖息于三个存在罕见迁移连接的岛屿的物种，开展了地理隔离物种形成所需时间的研究。本研究假设生殖遗传不相容性（genetic incompatibility）由多个数量基因座（quantitative loci）调控，且当个体间的基因座差异超过某一阈值时，二者无法发生基因交流。针对每个基因座，我们定义了地理构型（geographic configuration, GC）——即标注携带共同等位基因的岛屿的构型，并追踪了不同地理构型之间的随机转变过程。基于上述结果，我们计算了遗传距离的动态变化。由于单次迁移事件可为多个基因座的状态转变提供契机，不同基因座的地理构型之间存在相关性，这一相关性可通过构建携带不同地理构型的基因座数量的随机微分方程（stochastic differential equations）进行量化评估。我们的模型显示，较少的生殖不相容基因座数量可促进邻域物种形成（parapatric speciation）；与相同数量的单独迁移个体相比，集体抵达的迁移个体能够缩短物种形成的等待时长。此外，我们还探讨了物种形成速率随地理结构的变化规律。