Random interbreeding between cryptic lineages of the Common Raven: evidence for speciation in reverse

DNA sequence studies frequently reveal evidence of cryptic lineages in morphologically uniform species, many of which turn out to be evolutionarily distinct species. The Common Raven (Corvus corax) includes two deeply divergent mtDNA lineages: one lineage seems restricted to western North America and the other is Holarctic in distribution. These deep clades hint of the possibility of cryptic species in the western United States. We tested this hypothesis in a population consisting of an equal proportion of both mtDNA clades, by quantifying mating patterns and associated fitness consequences with respect to mtDNA. We also tested for morphological, behavioural and ecological correlates of sex and mtDNA clade membership. Mate pairings were random with respect to mtDNA clades, and there were no differences in reproductive success between assortatively and nonassortatively mated pairs. We found no differences in survival or resource use between clades. There were no differences in morphologi...DNA序列研究常可在形态学一致的物种中发现隐存谱系（cryptic lineage）的相关证据，其中多数谱系最终被鉴定为演化上独立的有效物种。渡鸦（Corvus corax）存在两个高度分化的线粒体DNA（mtDNA）谱系：其一仅局限分布于北美西部，另一谱系的分布范围则为全北界。这些深度演化支（clade）提示美国西部存在隐存物种的可能性。我们针对该假说开展了检验：以两类线粒体DNA谱系占比均等的种群为研究对象，通过量化交配模式及其伴随的线粒体DNA相关适合度效应进行验证；同时检验了性别与线粒体DNA谱系归属在形态学、行为学及生态学层面的相关性。研究结果显示，交配配对与线粒体DNA谱系之间呈随机模式，选型交配配对与非选型交配配对的繁殖成功率无显著差异。两谱系在存活率与资源利用模式上亦无差异。形态学上未发现差异……