Evolution of wing length and melanin-based coloration in insular populations of a cosmopolitan raptor

Aim. Insular populations face different conditions than those living on continents, thus resulting in the evolution of typical insular phenotypes, like smaller body sizes or reduced colourations. However, the generality of the so-called “island rule” has been questioned, and intraspecific analyses on the effects of insularity on cosmopolitan species are lacking. Here, we tested the predictions of the island rule in the cosmopolitan common barn owl group.

Location. World.

Taxon. Barn owl species complex.

Methods. We compared wing and bill length, as well as melanin-based plumage traits, between thousands of insular and continental barn owls living in the Afro-Palearctic region (T. alba), in the Americas (T. furcata), and in Australasia (T. javanica). We also tested whether the difference between insular and continental populations in these phenotypic traits varies among islands/archipelagos of different size and isolation.

Results. In all the regions, we found differences bet...

研究目的：岛屿种群与大陆种群所处环境条件迥异，由此演化出典型的岛屿表型，例如体型偏小、体色减淡等。然而，学界对所谓的岛屿法则（island rule）的普适性仍存质疑，且目前尚缺乏针对广布物种受岛屿效应影响的种内分析研究。本研究以广布的仓鸮类群为对象，对岛屿法则的相关预测进行了验证。
研究区域：全球范围。
研究类群：仓鸮物种复合体（barn owl species complex）。
研究方法：我们对比了分布于非洲-古北界（Afro-Palearctic region）、美洲（T. furcata）以及澳大拉西亚（Australasia）的数千只岛屿种群与大陆种群仓鸮的翅长、喙长，以及基于黑色素的羽毛特征；其中非洲-古北界类群为T. alba，美洲类群为T. furcata，澳大拉西亚类群为T. javanica。同时，我们还检验了不同面积与隔离程度的岛屿/群岛之间，岛屿与大陆种群的上述表型性状差异是否存在显著变化。
研究结果：在所有研究区域中，我们均发现了差异……