Data from: Disentangling the complex evolutionary history of the Western Palearctic blue tits (Cyanistes spp.) – phylogenomic analyses suggest radiation by multiple colonisation events and subsequent isolation

Isolated islands and their often unique biota continue to play key roles for understanding the importance of drift, genetic variation and adaptation in the process of population differentiation and speciation. One island system that has inspired and intrigued evolutionary biologists is the blue tit complex (Cyanistes spp.) in Europe and Africa, in particular the complex evolutionary history of the multiple genetically distinct taxa of the Canary Islands. Understanding Afrocanarian colonization events is of particular importance because of recent unconventional suggestions that these island populations acted as source of the widespread population in mainland Africa. We investigated the relationship between mainland and island blue tits using a combination of Sanger sequencing at a population level (20 loci; 12 500 nucleotides) and next-generation sequencing of single population representatives (>3 200 000 nucleotides), analysed in coalescence and phylogenetic frameworks. We found (i) that Afrocanarian blue tits are monophyletic and represent four major clades, (ii) that the blue tit complex has a continental origin and that the Canary Islands were colonized three times, (iii) that all island populations have low genetic variation, indicating low long-term effective population sizes and (iv) that populations on La Palma and in Libya represent relicts of an ancestral North African population. Further, demographic reconstructions revealed (v) that the Canary Islands, conforming to traditional views, hold sink populations, which have not served as source for back colonization of the African mainland. Our study demonstrates the importance of complete taxon sampling and an extensive multimarker study design to obtain robust phylogeographical inferences.

孤立岛屿及其常具独特性的生物区系，在解析遗传漂变、遗传变异与适应在种群分化和物种形成过程中的重要性时始终发挥着关键作用。分布于欧洲与非洲的蓝山雀复合类群（Cyanistes spp.）便是一组令进化生物学家着迷并从中获得研究灵感的岛屿研究系统，其中尤以加那利群岛内多个遗传分化类群的复杂演化历史为核心关注点。解析非洲-加那利群岛的拓殖事件具有特殊意义，因近期有非常规观点提出，这些岛屿种群曾作为非洲大陆广布种群的起源来源。本研究结合群体水平桑格测序（Sanger sequencing，20个基因座，共12500个核苷酸）与单种群代表样本的下一代测序（next-generation sequencing，>3200000个核苷酸），并基于溯祖与系统发育分析框架开展分析，以探究大陆与岛屿蓝山雀之间的演化关系。研究获得如下发现：（1）非洲-加那利群岛蓝山雀为单系群，可划分为4个主要支系；（2）蓝山雀复合类群起源于大陆，加那利群岛共经历3次拓殖事件；（3）所有岛屿种群的遗传变异水平均较低，提示其长期有效种群规模偏小；（4）拉帕尔马岛与利比亚的种群代表了北非祖先种群的孑遗类群；（5）种群历史重建分析显示，加那利群岛的种群符合传统认知，属于汇种群（sink populations），并未作为扩散源发生对非洲大陆的反向拓殖。本研究证实，完整的类群采样与多标记广泛测序的研究设计，对于获得可靠的系统生物地理学推断结论具有重要意义。