Island spotted skunks (Spilogale gracilis amphiala) are a rare subspecies endemic to the California Channel Islands, currently extant on Santa Cruz and Santa Rosa islands. How and when skunks arrived on the islands is unknown, hindering decision-making about their taxonomic status and conservation priority. We investigated these questions by sequencing the complete mitochondrial genomes of 55 skunks from the two islands and mainland (California and Arizona) and examining phylogenetic patterns and estimations of isolation times among populations. Island spotted skunks grouped in a single monophyletic clade distinct from mainland spotted skunks. A haplotype network analysis had the most recent common ancestral haplotype sampled from an individual on Santa Rosa, suggesting both islands were colonized by a single matriline. Additionally, no haplotypes were shared between skunk populations on the two islands. These patterns imply that both island populations were derived from a common ancestral population shortly after establishment and have remained isolated from each other ever since. Together with divergence estimates from three methods, this topology is consistent with colonization of the super-island, Santarosae, by a single ancestral population of spotted skunks in the early Holocene, followed by divergence as the sea level rose and split Santarosae into Santa Cruz and Santa Rosa islands 9,400–9,700 years ago. Such a scenario of colonization could be explained either by rafting or one-time transport by Native Americans. Given their distinct evolutionary history, high levels of endemism, and current population status, island spotted skunks may warrant management as distinct evolutionarily significant units.

中文翻译：

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加利福尼亚海峡群岛岛斑臭鼬线粒体分化的模式和时间

岛斑臭鼬（Spilogale gracilis amphiala）是加利福尼亚海峡群岛特有的稀有亚种，目前在圣克鲁斯岛和圣罗莎岛生存。臭鼬是如何以及何时到达这些岛屿的尚不清楚，这阻碍了有关它们的分类地位和保护优先级的决策。我们通过对来自两个岛屿和大陆（加利福尼亚州和亚利桑那州）的 55 只臭鼬的完整线粒体基因组进行测序并检查种群间的系统发育模式和隔离时间估计来研究这些问题。岛斑臭鼬属于单一的单系进化枝，与大陆斑臭鼬不同。单倍型网络分析从圣罗莎的一个人身上采集了最新的常见祖先单倍型，这表明这两个岛屿都被单一的母系殖民。此外，两个岛上的臭鼬种群之间没有共享单倍型。这些模式意味着两个岛屿人口在建立后不久都来自一个共同的祖先人口，并且从那以后一直彼此隔离。连同三种方法的差异估计，这种拓扑结构与超级岛屿 Santarosae 的殖民化一致，即在全新世早期，单一祖先​​的斑点臭鼬种群，随后随着海平面上升而出现分歧，并将 Santarosae 分裂为圣克鲁斯和圣罗莎群岛 9,400–9,700 年前。这种殖民化情景可以通过漂流或美洲原住民的一次性运输来解释。鉴于它们独特的进化历史、高度的特有性和当前的人口状况，