Data from: Reed frog diversification in the Gulf of Guinea: overseas dispersal, the progression rule, and in situ speciation

Oceanic islands accumulate endemic species when new colonists diverge from source populations or by in situ diversification of resident island endemics. The relative importance of dispersal versus in situ speciation in generating diversity on islands varies with a number of archipelago characteristics including island size, age, and remoteness. Here we characterize inter-island dispersal and in situ speciation in frogs endemic to the Gulf of Guinea islands. Using mitochondrial sequence and genome-wide SNP data we demonstrate that dispersal proceeded from the younger island (São Tomé) to the older island (Príncipe) indicating that for organisms that disperse overseas on rafts, dispersal between islands may be determined by ocean currents and not island age. We find that dispersal between the islands is not ongoing, resulting in genotypically distinct but phenotypically similar lineages on the two islands. Finally, we demonstrate that in situ diversification on São Tomé Island likely proceeded in allopatry due to the geographic separation of breeding sites, resulting in phenotypically distinct species. We find evidence of hybridization between the species where their ranges are sympatric and the hybrid zone coincides with a transition from agricultural land to primary forest, indicating that anthropogenic development may have facilitated secondary contact between previously allopatric species.

大洋岛屿在新拓殖种群与源种群发生分化时，或通过栖息于岛上的特有类群发生原地分化时，会积累特有物种。岛屿生物多样性产生过程中，拓殖与原位成种的相对重要性，受群岛的多项特征影响，包括岛屿面积、形成年代与隔离程度。本研究对几内亚湾群岛特有蛙类的岛间拓殖与原位成种过程进行了表征。我们利用线粒体序列与全基因组单核苷酸多态性（SNP）数据证实，拓殖方向是从较年轻的圣多美岛流向较年老的普林西比岛，这表明对于依靠筏体跨洋扩散的生物而言，岛屿间的拓殖可能由洋流决定，而非岛屿形成年代。我们发现，岛屿间的拓殖已不再持续，导致两座岛屿上形成了遗传背景迥异但表型相似的支系。最后，我们证实圣多美岛上的原地分化很可能通过繁殖位点的地理隔离实现异域成种，进而产生了表型各异的物种。我们发现，在物种的同域分布区域存在杂交现象，且杂交带与农田向原始森林的过渡区域重合，这表明人为开发可能促进了原本异域分布的物种发生二次接触。