由于缺乏大陆捕食者且资源竞争减少，在岛屿上孤立生活的动物往往会进化出独特的特征，这被称为“岛屿综合征”。小动物经常变得更大——这种现象被称为岛屿巨型化，正如毛里求斯的渡渡鸟，它从鸽子的大小进化到了大火鸡的大小。最近发表在《林奈学会进化杂志》上的一项研究表明，苏格兰圣基尔达和设得兰群岛上的某些鹪鹩亚种已经发展出了这种综合征，在与英国大陆隔绝数千年后，它们进化得比大陆亲戚大得多。
为了系统地分析这一进化变化，研究人员利用雾网和声音录音在设得兰、公平岛、外赫布里底和圣基尔达捕获了45只具有领地意识的鹪鹩。他们将这些鸟类与苏格兰国家博物馆的历史标本、英国鸟类学信托基金会的体重数据以及其他695对岛屿-大陆鸟类进行了对比。研究发现，虽然公平岛和外赫布里底的鹪鹩与大陆鸟类大小相似或略大，但圣基尔达和设得兰的鹪鹩却非常巨大。事实上，最大的岛屿鹪鹩的重量是最小大陆鹪鹩的两倍，这使它们跻身有记录以来最极端的岛屿巨型化案例的前25%。
除了体型更大之外，与大陆同类相比，圣基尔达和设得兰的鹪鹩还进化出了独特的歌声。基因分析显示，尽管这两个岛屿种群都进化出了相似的巨型特征，但它们之间控制体型的基因重合比例却很小。这一发现表明，圣基尔达和设得兰的鹪鹩经历了平行进化，通过不同的遗传途径进化出了巨大的体型。虽然岛屿巨型化（或矮小化）的确切进化驱动因素仍不清楚，但这些苏格兰鹪鹩为解开这一谜团提供了宝贵的基因线索。
Animals isolated on islands often evolve distinct characteristics, known as "island syndromes," due to the absence of mainland predators and reduced resource competition. Small animals frequently become larger—a phenomenon called island gigantism, as seen in the Mauritius dodo, which grew from the size of a pigeon to a large turkey. A recent study published in the Evolutionary Journal of the Linnean Society reveals that certain subspecies of wrens on the Scottish archipelagoes of St Kilda and Shetland have developed this syndrome, having evolved to be much larger than their mainland relatives after being cut off from mainland Britain for thousands of years.
To systematically analyze this evolutionary change, researchers used mist nets and vocal recordings to capture 45 territorial wrens across Shetland, Fair Isle, the Outer Hebrides, and St Kilda. They compared these birds with historical specimens from the National Museums Scotland, body-mass data from the British Trust for Ornithology, and 695 other island-mainland bird pairs. The study found that while Fair Isle and Outer Hebrides wrens were similar or slightly larger than mainland birds, the St Kilda and Shetland wrens were gigantic. Indeed, the largest island wren weighed twice as much as the smallest mainland wren, placing them in the top 25% of the most extreme cases of island gigantism ever recorded.
In addition to their larger size, the St Kilda and Shetland wrens developed distinctive songs compared to their mainland counterparts. Genetic analysis revealed that despite both island populations developing similar gigantism, only a small portion of the genes regulating body size overlapped between them. This finding indicates that the St Kilda and Shetland wrens underwent parallel evolution, developing their large sizes through separate genetic pathways. While the exact evolutionary drivers of island gigantism and dwarfism remain unclear, these Scottish wrens offer valuable genomic clues to help solve the mystery.
Source: Some Scottish wrens are a striking case of “island syndrome”
Subtitle: They have got much bigger than their mainland cousins
Dateline: Jul 09, 2026 06:30 AM