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 rearrangemen...