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中一种高效且应用广泛的方法。然而，区分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，仅能纳入先验上更受关注的备选情景。尽管该做法通常具有合理性，但会遗漏那些虽未被预先考虑、却可能得到充分支持的种群历史情景。本研究采用分层锦标赛方法：首轮ABC分析中对不同情景子集进行比较，将胜出情景纳入第二轮分析，以此重构古北界西部栎瘿蜂（Synergus umbraculus，膜翅目，瘿蜂科）的种群历史。我们利用7个基因座上总计4233 bp的序列数据，探究了伊比利亚半岛、意大利、巴尔干半岛及西亚4个推定更新世避难所种群之间的演化关系。我们在8个分组中比较了148种备选情景的支持度，每个分组均包含4个种群在给定亲缘关系拓扑结构下的所有重排组合，同时考虑是否存在单一种群的基因混合起源，以及是否存在未采样的“幽灵”种群。研究结果显示，此前针对其他瘿蜂类群推断出的“自东向外”定向扩散情景几乎未得到支持。与之相反，支持度最高的模型表明：更新世晚期，伊比利亚半岛种群是首个与其他区域种群发生分化的类群；随后巴尔干半岛与西亚种群产生分化；意大利种群则是由伊比利亚与巴尔干种群在更新世晚期经基因混合形成。我们将本研究结果与栎瘿群落其他类群的已知研究进行对比，并探讨了采用锦标赛方法探索系统地理学模型空间的优势与局限。