Some Aspects of Ecology and Ontogeny in the Fishes and Amphibians

Abstract

Although long tradition combines the study of amphibians and reptiles into one field, these two vertebrate classes are usually treated entirely separately, in actual practice, even when both are discussed in the same paper. Comparative papers on amphibians and reptiles are rare, except for those that inquire into basic evolutionary problems from the paleontological viewpoint. Typically, we specialize in details and overlook the broadly comparative problems that cross departmental and taxonomic lines. Perhaps discussion of some of the opportunities offered by a different and less familiar combination of taxonomic groups can make the advantages of interdepartmental study more tangible. The fishes and amphibians invite such comparative study, for these two classes present some important common problems in life history and evolutionary biology. Effective comparison of fish and amphibian life histories is somewhat hampered by numerical and ecological differences. The Recent amphibians are remnants of a once very large and complex group, but the Recent fishes represent a continuing great diversification of a long-dominant group. Furthermore, the fishes are aquatic throughout life, but most amphibians have, in addition, both the advantages and the problems of terrestrial life during part of their ontogeny. Within the limits imposed by such differences, however, much can be learned from comparative studies on life history patterns and on developmental characters, in relation to the varied ecological situations that these animals face. We commonly base ecological and distributional studies on the adult stage only, and overlook the possibility that the relative success or failure of a species may be determined largely by events that affect its early developmental stages, rather than its more conspicuous adult. The critical importance of survival rate in early stages is recognized most clearly by fishery biologists, who are concerned with size of population of commercial