Evolutionary Studies of Morphological Diversity in Salamander Limbs

脊椎动物的肢体大约在5亿年前由高级鱼类的鳍进化而来。尽管经历了如此漫长的时间，脊椎动物四肢的进化却极其规律——某些模式经常重复出现，而其他模式则从未出现过。许多研究者认为，发育机制可能限制了不同物种可能发生的进化变化。这一建议侧重于最原始的有肢动物群体——蝾螈——的发展和进化多样性之间的关系。比较和实验研究将启发蝾螈肢体的进化史在多大程度上受到发育机制的限制。特别是，将分析体型、关键发育事件的发生时间和进化多样性之间的关系。对发育和成年四肢的比较研究将揭示蝾螈手和脚的骨骼元素模式进化的规律。实验研究将揭示发育机制对这些规律负责的方式。肢体进化的许多规律可能与发育中的胚胎和幼虫的大小有关。体型的变化是蝾螈进化的一个重要趋势。身体大小将通过化学和外科治疗的实验来控制，以探索身体大小和骨骼模式在蝾螈四肢中的作用。这些研究将阐明一个重要的限制，身体大小，在蝾螈肢体进化的作用。

The vertebrate limb arose approximately five hundred million years ago from the fins of advanced fish. Despite this enormous amount of time, the evolution of the limbs of vertebrate animals has been extremely regular--certain patterns frequently recur, other patterns are never encountered. Many workers have suggested that the mechanisms of development may limit the amount of evolutionary change possible in different species. This proposal focuses on the relationships between development and evolutionary diversity in the most primitive living group of limbed animals--salamanders. Comparative and experimental studies will enlighten the extent to which the evolutionary history of the salamander limb has been limited by developmental mechanisms. In particular, the relationship between body size, the timing of key developmental events, and evolutionary diversity will be analyzed. Comparative studies of developing and adult limbs will reveal the regularities seen in the evolution of the pattern of bony elements of the hands and feet of salamanders. Experimental studies will reveal the manner in which developmental mechanisms are responsible for these regularities. Many of the regularities seen on limb evolution may be related to the size of the developing embryo and larva. Changes in body size are an important trend in salamander evolution. Body size will be experimentally manipulated through both chemical and surgical treatments to explore the role of body size and the pattern of bones in salamander limbs. These studies will elucidate the role of an important constraint, body size, on salamander limb evolution.