Department of Biology, University of Rochester, RC Box 270211, Rochester, NY 14627, USA.
Mol Ecol. 2011 Dec;20(23):4823-6. doi: 10.1111/j.1365-294X.2011.05257.x.
If island biogeography has a sweet spot, it's where islands generate their own species diversity rather than merely taking on mainland immigrants. In birds and other highly dispersive taxa, however, this 'zone of radiation', may be vanishingly small. Darwin's finches and Hawaiian Honeycreepers are among only a handful of examples of island radiation in birds (Price 2008), suggesting that winged powers of dispersal make sufficient isolation from mainland colonists unlikely, while also hindering speciation within and among isolated islands. Nevertheless, two studies in this issue of Molecular Ecology join a string of other recent analyses suggesting that island radiation in birds remains under-appreciated (see also Moyle et al. 2009; Kisel & Barraclough 2010; Rosindell & Phillimore 2011). Melo et al. (2011) use a phylogenetic analysis of white-eyes on islands in the Gulf of Guinea to identify two previously overlooked island radiations, and reveal replicated adaptive divergence on islands where species occur in pairs. Sly et al. (2011), meanwhile, consider possible explanations for speciation and geographic differentiation within a large island, and find the same type of oceanic barriers that are critical to bird speciation across archipelagos may also contribute to divergence that appears to have occurred within a single island.
如果说岛屿生物地理学有一个“甜蜜点”，那就是岛屿产生自身物种多样性的地方，而不是仅仅接受大陆移民。然而，在鸟类和其他高度扩散的分类群中，这个“辐射区”可能非常小。达尔文雀和夏威夷蜜旋木雀是鸟类中仅有的少数几个岛屿辐射的例子之一（Price 2008），这表明翅膀的扩散能力使得它们与大陆殖民者充分隔离的可能性很小，同时也阻碍了岛屿内部和岛屿之间的物种形成。尽管如此，本期《分子生态学》中的两项研究加入了一系列其他最近的分析，表明鸟类的岛屿辐射仍然被低估了（另见 Moyle 等人，2009 年；Kisel 和 Barraclough，2010 年；Rosindell 和 Phillimore，2011 年）。Melo 等人（2011 年）对白眼鸟在几内亚湾岛屿上的系统发育分析，确定了两个以前被忽视的岛屿辐射，并揭示了在物种成对出现的岛屿上发生的重复适应性分歧。与此同时，Sly 等人（2011 年）考虑了物种形成和一个大岛屿内部地理分化的可能解释，发现对整个群岛的鸟类物种形成至关重要的海洋屏障，也可能导致似乎在单个岛屿内发生的分化。
