Brusatte Stephen L, Lloyd Graeme T, Wang Steve C, Norell Mark A
School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JW, UK.
Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK.
Curr Biol. 2014 Oct 20;24(20):2386-92. doi: 10.1016/j.cub.2014.08.034. Epub 2014 Sep 25.
The evolution of birds from theropod dinosaurs was one of the great evolutionary transitions in the history of life. The macroevolutionary tempo and mode of this transition is poorly studied, which is surprising because it may offer key insight into major questions in evolutionary biology, particularly whether the origins of evolutionary novelties or new ecological opportunities are associated with unusually elevated "bursts" of evolution. We present a comprehensive phylogeny placing birds within the context of theropod evolution and quantify rates of morphological evolution and changes in overall morphological disparity across the dinosaur-bird transition. Birds evolved significantly faster than other theropods, but they are indistinguishable from their closest relatives in morphospace. Our results demonstrate that the rise of birds was a complex process: birds are a continuum of millions of years of theropod evolution, and there was no great jump between nonbirds and birds in morphospace, but once the avian body plan was gradually assembled, birds experienced an early burst of rapid anatomical evolution. This suggests that high rates of morphological evolution after the development of a novel body plan may be a common feature of macroevolution, as first hypothesized by G.G. Simpson more than 60 years ago.
鸟类从兽脚亚目恐龙进化而来，是生命史上重大的进化转变之一。人们对这一转变的宏观进化节奏和模式研究甚少，这令人惊讶，因为它可能为进化生物学的重大问题提供关键见解，特别是进化新奇性或新生态机遇的起源是否与异常加速的“爆发式”进化相关。我们构建了一个全面的系统发育树，将鸟类置于兽脚亚目恐龙的进化背景中，并量化了恐龙向鸟类过渡过程中的形态进化速率以及整体形态差异的变化。鸟类的进化速度明显快于其他兽脚亚目恐龙，但在形态空间上与它们的近亲并无差异。我们的研究结果表明，鸟类的崛起是一个复杂的过程：鸟类是数百万年兽脚亚目恐龙进化的延续，在形态空间上，非鸟类和鸟类之间没有巨大的跳跃，但一旦鸟类的身体结构逐渐形成，它们就经历了早期的快速解剖学进化爆发。这表明，正如60多年前G.G. 辛普森首次提出的假设那样，新身体结构形成后的高形态进化速率可能是宏观进化的一个共同特征。
