Data from: Migration, mitochondria, and the yellow-rumped warbler

Discordance between mitochondrial and nuclear DNA has been noted in many systems. Asymmetric introgression of mitochondria is a common cause of such discordances, although in most cases the drivers of introgression are unknown. In the yellow-rumped warbler, evidence suggests that mtDNA from the eastern, myrtle warbler, has introgressed across much of the range of the western form, the Audubon's warbler. Within the southwestern United States myrtle mtDNA comes into contact with another clade that occurs in the Mexican black-fronted warbler. Both northern forms exhibit seasonal migration, whereas black-fronted warblers are nonmigratory. We investigated the link between mitochondrial introgression, mitochondrial function, and migration using novel genetic, isotopic, biochemical, and phenotypic data obtained from populations in the transition zone. Isotopes suggest the zone is coincident with a shift in migration, with individuals in the south being resident and populations further north becoming increasingly more migratory. Mitochondrial respiration in flight muscles demonstrates that myrtle-type individuals have a significantly greater acceptor control ratio of mitochondria, suggesting it may be more metabolically efficient. To our knowledge this is the first time this type of intraspecific variation in mitochondrial respiration has been measured in wild birds and we discuss how such mitochondrial adaptations may have facilitated introgression.

线粒体DNA与核DNA之间的不一致现象已在诸多类群中被报道。不对称线粒体基因渐渗是引发此类不一致的常见诱因，尽管多数情况下渐渗的驱动因素尚未明确。在黄腰林莺（yellow-rumped warbler）中，已有证据显示，东部类群桃颊林莺（myrtle warbler）的线粒体DNA（mitochondrial DNA, mtDNA）已在西部类群奥杜邦林莺（Audubon's warbler）的大部分分布范围内发生渐渗。在美国西南部地区，桃颊林莺的线粒体DNA与墨西哥黑额林莺（Mexican black-fronted warbler）所属的另一演化支发生接触。两种北部类群均具季节性迁徙习性，而黑额林莺则为留鸟。本研究借助来自过渡带种群的全新遗传、同位素、生化与表型数据，探究了线粒体渐渗、线粒体功能与迁徙行为之间的关联。同位素分析结果表明，该过渡带与迁徙行为的转变高度吻合：南部个体为留鸟，往北的种群迁徙性逐渐增强。飞行肌线粒体呼吸实验显示，桃颊林莺型个体的线粒体受体控制比（acceptor control ratio）显著更高，提示其代谢效率可能更优。据我们所知，这是首次在野生鸟类中开展此类种内线粒体呼吸变异的检测，我们还探讨了此类线粒体适应性可能如何促进了基因渐渗。