Data from: Females drive asymmetrical introgression from rare to common species in Darwin's tree finches

The consequences of hybridization for biodiversity depend on the specific ecological and evolutionary context in which it occurs. Understanding patterns of gene flow among hybridizing species is crucial for determining the evolutionary trajectories of species assemblages. The recently discovered hybridization between two species of Darwin's tree finches (Camarhynchus parvulus and C. pauper) on Floreana Island, Galápagos, presents an exciting opportunity to investigate the mechanisms causing hybridization and its potential evolutionary consequences under conditions of recent habitat disturbance and the introduction of invasive pathogens. In this study, we combine morphological and genetic analysis with pairing observations to explore the extent, direction and drivers of hybridization and to test if hybridization patterns are a result of asymmetrical pairing preference driven by females of the rarer species (C. pauper). We found asymmetrical introgression from the critically endangered, larger-bodied C. pauper to the common, smaller-bodied C. parvulus, which was associated with a lack of selection against heterospecific males by C. pauper females. Examination of pairing data showed that C. parvulus females paired assortatively while C. pauper females showed no such pattern. This study shows how sex-specific drivers can determine the direction of gene flow in hybridizing species. Furthermore, our results suggest the existence of a hybrid swarm comprised of C. parvulus and hybrid birds. We discuss the influence of interspecific abundance differences and susceptibility to the invasive parasite Philornis downsi on the observed hybridisation and recommend that the conservation of this iconic species group should be managed jointly rather than species-specific. Usage Notes Peters et al. GenotypeDataAllele size data for tree finches on Floreana Island, Galapagos "Ring#" refers to the identifier inscribed on an aluminum band around a bird's tarsus. ‘Cluster’ refers to population assignment based on analyses of microsatellite loci using the program STRUCTURE (C. parvulus, Hybrid, C. pauper). Remaining information refers to allele size (maximum height at peak of allele) at each of nine microsatellite loci (Gf01, Gf03, Gf04, Gf05, Gf06, Gf07, Gf11, Gf12, Gf13)Peters et al. MorphologyDataMorphological measurements of tree finches sampled on Floreana Island, Galápagos in 2004, 2005, 2006, 2008, 2010, 2012, 2013 and 2014. Techniques for measuring morphological variables are described in the associated manuscript. ‘Putative population’ refers to assignment based on morphology for exploratory analyses (see associated manuscript and supplementary material). ‘Cluster’ and ‘Membership Coefficient’ refers to population assignment based on analyses of microsatellite loci (using the program STRUCTURE).Peters et al. PairingDataAssortative pairing, genetic and morphological data for male and female tree finches sampled on Floreana Island, Galapagos, 2005, 2010, 2012, 2014 and 2014. Techniques for measuring morphological features are described in the associated manuscript. ‘Cluster’, ‘Cluster_2’ and ‘Membership Coefficient’ refers to population assignment based on analyses of microsatellite loci (using the program STRUCTURE).

杂交（hybridization）对生物多样性的影响取决于其发生的特定生态与进化背景。解析杂交物种间的基因流（gene flow）模式，对于明确物种类群的进化轨迹至关重要。
近期在加拉帕戈斯群岛弗洛雷亚纳岛（Floreana Island）发现的两种达尔文树雀（Darwin's tree finches）——小树雀（Camarhynchus parvulus）与贫嘴树雀（C. pauper）——之间的杂交事件，为探究近期生境干扰与入侵病原引入背景下，杂交发生的机制及其潜在进化后果提供了绝佳研究契机。
本研究结合形态学、遗传学分析与配对行为观测，旨在探究杂交的发生范围、方向与驱动因素，并验证杂交模式是否由稀有物种（C. pauper）雌性的不对称配对偏好所导致。
本研究发现，从体型较大且处于极危状态的C. pauper到常见的体型较小的C. parvulus存在不对称基因渐渗（asymmetrical introgression），这一现象与C. pauper雌性未对异种雄性产生排斥选择有关。配对数据分析显示，C. parvulus雌性存在选型配对（assortative pairing）行为，而C. pauper雌性则未表现出该模式。
本研究揭示了性别特异性驱动因素如何决定杂交物种间的基因流方向。此外，研究结果表明存在由C. parvulus与杂交个体组成的杂交群（hybrid swarm）。
本研究探讨了物种种间丰度差异以及对入侵寄生蝇（Philornis downsi）的易感性对观测到的杂交现象的影响，并建议对这一标志性类群的保护应采取联合管理策略，而非针对单一物种进行保护。

使用说明
彼得斯等（Peters et al.） 基因型数据
加拉帕戈斯群岛弗洛雷亚纳岛树雀的等位基因长度数据。"Ring#"指鸟类跗跖上铝制脚环的编号。"Cluster（类群）"指基于微卫星位点（microsatellite loci）分析、通过STRUCTURE软件进行的种群归属划分（分为C. parvulus、杂交个体、C. pauper三类）。其余信息为9个微卫星位点（Gf01、Gf03、Gf04、Gf05、Gf06、Gf07、Gf11、Gf12、Gf13）的等位基因长度（等位基因峰的最大高度）。

彼得斯等（Peters et al.） 形态学数据
2004、2005、2006、2008、2010、2012、2013及2014年在加拉帕戈斯群岛弗洛雷亚纳岛采集的树雀形态测量数据。形态学变量的测量方法详见相关论文。"Putative population（推定种群）"指基于形态学进行的探索性分析种群归属（详见相关论文及补充材料）。"Cluster（类群）"与"Membership Coefficient（归属系数）"指基于微卫星位点分析、通过STRUCTURE软件得到的种群归属结果。

彼得斯等（Peters et al.） 配对行为数据
2005、2010、2012、2014及2014年在加拉帕戈斯群岛弗洛雷亚纳岛采集的雌雄树雀的选型配对、遗传学与形态学数据。形态特征的测量方法详见相关论文。"Cluster（类群）"、"Cluster_2（类群2）"与"Membership Coefficient（归属系数）"指基于微卫星位点分析、通过STRUCTURE软件得到的种群归属结果。