Mercure Alan, Ralls Katherine, Koepfli Klaus P, Wayne Robert K
Department of Biology, University of California, Los Angeles, California, 90024.
Evolution. 1993 Oct;47(5):1313-1328. doi: 10.1111/j.1558-5646.1993.tb02157.x.
Gene flow can effectively suppress genetic divergence among widely separated populations in highly mobile species. However, the same may not be true of species that typically disperse over shorter distances. Using mtDNA restriction-site and sequence analyses, we evaluate the extent of divergence among populations of two small relatively sedentary North American canids, the kit and swift foxes (genus Vulpes). We determine the significance of genetic differentiation among populations separated by distance and those separated by discrete topographic barriers. Our results show the among-population component of genetic variation in kit and swift foxes is large and similar to that of small rodents with limited dispersal ability. In addition, we found two distinct groupings of genotypes, separated by the Rocky Mountains, corresponding to the traditional division between kit and swift fox populations. Previous workers have characterized these morphologically similar populations either as separate species or subspecies. Our mtDNA data also suggest that kit and swift fox populations hybridize over a limited geographic area. However, the sequence divergence between kit and swift foxes is similar to that between these taxa and the arctic fox (Alopex lagopus), a morphologically distinct species commonly placed in a separate genus. This result presents a dilemma for species concepts, and we conclude that kit and swift foxes should be recognized as separate species.
基因流动能够有效抑制高迁移性物种中广泛分布的种群之间的遗传分化。然而，对于通常短距离扩散的物种而言，情况可能并非如此。我们利用线粒体DNA（mtDNA）限制性酶切位点和序列分析，评估了两种相对定居的小型北美犬科动物——敏狐和草原狐（狐属）种群之间的分化程度。我们确定了因距离分隔以及因离散地形屏障分隔的种群之间遗传分化的显著性。我们的研究结果表明，敏狐和草原狐种群间遗传变异的组成部分很大，且与扩散能力有限的小型啮齿动物相似。此外，我们发现由落基山脉分隔的两个不同的基因型分组，这与敏狐和草原狐种群之间的传统划分相对应。先前的研究人员将这些形态相似的种群要么归类为不同的物种，要么归类为不同的亚种。我们的线粒体DNA数据还表明，敏狐和草原狐种群在有限的地理区域内杂交。然而，敏狐和草原狐之间的序列差异与这些分类单元和北极狐（Alopex lagopus）之间的差异相似，北极狐是一种形态上有明显区别的物种，通常被置于一个单独的属中。这一结果给物种概念带来了难题，我们得出结论，敏狐和草原狐应被视为不同的物种。
