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效能突出且应用广泛的方法。然而，用于甄别不同历史情景所需的计算成本，往往限制了可比较的情景范围，仅能涵盖先验上被认为更具可能性的候选情景。该做法虽常具备合理性，但会遗漏那些虽出乎意料却得到充分支持的种群历史情景。本研究采用层级锦标赛式分析方法，即先在第一轮ABC分析中对比子集情景，再将胜出情景纳入第二轮分析，以此重建西古北区内栎瘿蜂*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，探究了伊比利亚、意大利、巴尔干与西亚这4个推测的更新世避难所种群间的演化关系。我们在8个分析池中比较了148种备选情景的支持度，每个分析池包含4个种群在给定演化拓扑下的所有可能重排组合，并分别考虑是否存在通过遗传混合完成某一种群奠基的事件，以及是否存在未被采样的“幽灵”种群。研究结果显示，此前针对其他瘿蜂类群推断的“自东向外”定向扩散情景几乎未得到本研究支持。与之相反，支持度最高的模型表明：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，随后巴尔干与西亚种群发生分化，而意大利种群则是通过更新世晚期伊比利亚与巴尔干种群的遗传混合形成的。我们将本研究结果与栎瘿群落其他类群的已知研究结果进行了对比，并探讨了采用锦标赛式方法探索系统地理模型空间的优势与局限。