Evolutionary Studies of Morphological Diversity in Salamander Limbs

点击翻译按钮获取中文摘要

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.