DIVERSITY AND CONVERGENCE IN THE STUDY OF ORGANISMAL FUNCTION

ABSTRACT

Similarity of structure among organisms reflects either common ancestry or convergence. The latter indicates that natural selection has had a significant influence and therefore that the structure is of functional importance. Since natural selection is most directly felt at the organismal level of organization, convergence is most pervasive there. While such convergence provides evidence of adaptation for the evolutionary biologist, for the comparative physiologist it is a tool of much greater importance. It provides a way to distinguish at least initially between characters that matter and characters that do not, it permits evaluation of the degree of precision necessary for a character, and it improves the predictive value of generalizations about functional significance. Using convergence requires direct access to biological diversity; it also requires reliable phylogenetic information, the latter even more dependent on access to diverse material.