BODY AND LIMB SIZE DISSOCIATION AT THE ORIGIN OF BIRDS: UNCOUPLING ALLOMETRIC CONSTRAINTS ACROSS A MACROEVOLUTIONARY TRANSITION
BODY AND LIMB SIZE DISSOCIATION AT THE ORIGIN OF BIRDS: UNCOUPLING ALLOMETRIC CONSTRAINTS ACROSS A MACROEVOLUTIONARY TRANSITION
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DOI：
10.1111/evo.12150
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发表时间：
2013-09-01
期刊：
影响因子：
3.3
通讯作者：
Larsson, Hans C. E.
中科院分区：
文献类型：
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作者：
Dececchi, T. Alexander;Larsson, Hans C. E.
鸟类和动力飞行的起源是一个经典的重大进化转变。对它们起源的研究往往集中在翅膀的进化上，前肢伸长的趋势可以追溯到许多非鸟类的猛龙恐龙。我们提出的证据表明，鸟类前肢的相对伸长主要是由于异速生长，而不是由身体尺寸的减小所驱动的。一旦身体大小被考虑在内，在鸟类起源之前，没有增加前肢长度的趋势。我们报道了早期鸟类和非鸟类兽足类动物在前肢和后肢骨骼中具有显著不同的伸缩关系。祖先的前肢和后肢与身体大小的异速生长比例在鸟类起源时迅速分离，当翅膀显著伸长时，通过从祖先负的异速生长模式进化出与身体大小的正异速生长关系，通过保持类似的、接近的等长关系但截距减少，腿显著缩短。这些结果对动力飞行的进化和鸟类的早期多样化具有重要意义。他们提出，它们的四肢长度首先必须从一般的身体尺寸调整中分离出来，然后才能扩展到当今鸟类存在的广泛的前后肢形状和大小。
The origin of birds and powered flight is a classic major evolutionary transition. Research on their origin often focuses on the evolution of the wing with trends of forelimb elongation traced back through many nonavian maniraptoran dinosaurs. We present evidence that the relative forelimb elongation within avian antecedents is primarily due to allometry and is instead driven by a reduction in body size. Once body size is factored out, there is no trend of increasing forelimb length until the origin of birds. We report that early birds and nonavian theropods have significantly different scaling relationships within the forelimb and hindlimb skeleton. Ancestral forelimb and hindlimb allometric scaling to body size is rapidly decoupled at the origin of birds, when wings significantly elongate, by evolving a positive allometric relationship with body size from an ancestrally negative allometric pattern and legs significantly shorten by keeping a similar, near isometric relationship but with a reduced intercept. These results have implications for the evolution of powered flight and early diversification of birds. They suggest that their limb lengths first had to be dissociated from general body size scaling before expanding to the wide range of fore and hindlimb shapes and sizes present in today's birds.