The use of functional and adaptive criteria in phylogenetic systematics

Abstract

SYNOPSIS. The controversy over whether functional data can contribute to phylogenetic inference has grown in recent years. Steps can be taken toward its resolution if the relevance of functional data is judged for each component of phylogenetic analysis. These components are (1)recognizing of basic taxa (species or supraspecific taxa), (2) formulating hypotheses of homology followed by character analysis, (3) evaluating character phylogeny, (4) formulating phylogenetic hypotheses, and (5) evaluating alternative phylogenetic hypotheses. It can be shown that functional data do not play a necessary or unique role in any of these components of phylogenetic analysis. Arguments to the contrary have failed to provide a rigorous, repeatable methodto incorporate functional data; proponents of a functional approach to phylogenetic reconstruction rely too often on subjective, authoritarian argumentation.Students of functional evolutionary morphology frequently have failed to understand the kinds of information necessary to study or apply the causal process of adaptation via natural selection. This information, required by the very nature of the theory itself, includes knowing the pattern of heredity of the phenotypic characters being studied, relating intrapopulational phenotypic variability to variation in fitness, and knowing a sufficient amount about population structure to specify the components of natural selection. Studies within functional evolutionary morphology are not designed to satisfy these requirements. Functional evolutionary morphology uses the concepts of adaptation and natural selection axiomatically, and thus such studies contribute nothing to our understanding of the evolutionary process because hypotheses about that process are not being evaluated. This also suggests that, if functional evolutionary morphology wishes to engage in analyses of the evolutionary dynamics of the phenotype, a reorientation of its research strategy and goals will be necessary. © 1981 by the American Society of Zoologists.