A Rational Basis for a Priori Character Weighting

Abstract

Previously presented arguments for and against character weighting in systematic analyses are briefly reviewed and the bases for different weighting methods summarized. A priori and a posteriori methods are defined. I conclude that a priori weighting is the only noncircular approach for weighting of characters in the construction or recognition of groups of taxa, but that no objective method of a priori weighting has been proposed to date. A hy- pothetico-deductive methodology for character analysis completely prior to and independent of cladistic analysis (or phylogeny reconstruction) is briefly summarized. Identifications and characters are shown to be hypotheses testable prior to the construction of a cladogram. In that context, rather than attempting to weight on intrinsic properties of characters as suggested up to now, weighting on the basis of the relative degree of corroboration of the character in the character analysis provides a rational basis for character weighting if character conflicts occur in the cladistic analysis. (Character analysis; cladistic analysis; character weighting; phylogenetic analysis.) Two questions have traditionally been addressed in the evaluation of character weighting methods in systematic analysis. One is: can we judge the importance or reliability of a character's contribution to our estimates of relationships among taxa and, if so, how can we do so? The second question is: even if we can judge a char-