Data from: Tournament ABC analysis of the western palaearctic population history of an oak gallwasp, Synergus umbraculus

Approximate Bayesian computation (ABC) is a powerful and widely used approach in inference of population history. However, the computational effort required to discriminate among alternative historical scenarios often limits the set that is compared to those considered more likely a priori. While often justifiable, this approach will fail to consider unexpected but well-supported population histories. We used a hierarchical tournament approach, in which subsets of scenarios are compared in a first round of ABC analyses and the winners are compared in a second analysis, to reconstruct the population history of an oak gallwasp, Synergus umbraculus (Hymenoptera, Cynipidae) across the Western Palaearctic. We used 4233 bp of sequence data across 7 loci to explore the relationships between four putative Pleistocene refuge populations in Iberia, Italy, the Balkans, and Western Asia. We compared support for 148 alternative scenarios in eight pools, each pool comprising all possible rearrangements of four populations over a given topology of relationships, with or without founding of one population by admixture and with or without an unsampled ‘ghost’ population. We found very little support for the directional ‘out of the east’ scenario previously inferred for other gallwasp community members. Instead, the best-supported models identified Iberia as the first regional population to diverge from the others in the late Pleistocene, followed by divergence between the Balkans and Western Asia, and founding of the Italian population through late Pleistocene admixture from Iberia and the Balkans. We compare these results with what is known for other members of the oak gall community, and consider the strengths and weaknesses of using a tournament approach to explore phylogeographic model space.近似贝叶斯计算（Approximate Bayesian Computation, ABC）是种群历史推断领域一种高效且应用广泛的方法。然而，甄别不同历史情景所需的计算成本，往往将可比较的情景范围限制在先验层面更受关注的少数选项中。尽管该策略通常具备合理性，但会遗漏那些虽出乎意料却得到充分支撑的种群历史。我们采用层级锦标赛策略：首轮近似贝叶斯计算分析中先比较各情景子集，再将胜出情景纳入第二轮分析，以此重构西古北区栎瘿蜂——*Synergus umbraculus*（膜翅目，瘿蜂科）的种群历史。我们使用覆盖7个基因座的4233 bp序列数据，探究伊比利亚、意大利、巴尔干半岛与西亚这4个推测的更新世避难所种群间的演化关系。我们在8个情景池中对比了148种备选情景的支持度，每个情景池均包含给定关系拓扑下4个种群的所有重排组合，且分别设置“是否通过基因混合奠基某一种群”与“是否存在未采样‘幽灵’种群”两种变量组合。研究发现，此前针对其他瘿蜂类群推断出的“自东向外”定向演化情景几乎未获得支持。相反，支持度最高的模型显示：更新世晚期伊比利亚种群是首个与其他区域种群分化的区域性种群，随后巴尔干半岛与西亚种群发生分化，而意大利种群则是更新世晚期由伊比利亚和巴尔干半岛种群通过基因混合奠基形成的。我们将本研究结果与栎瘿蜂类群其他成员的已有研究结论进行对比，并探讨了采用锦标赛策略探索系统地理学模型空间的优势与局限。