A METHOD FOR DEDUCING BRANCHING SEQUENCES IN PHYLOGENY

Abstract

With the advent of relatively objective classifications, such as the phenetic classifications produced by the operational techniques of numerical taxonomy (Sokal and Sneath, 1963), it was inevitable that biologists would wonder what phylogenetic conclusions could be drawn from them and with what reliability.If these phenetic taxonomies did not reflect all of the elements of phyletics (Sokal and Camin, 1965), could techniques be devised for deducing the latter?For example, could operational methods be devised for deducing the cladistic relationships among taxa, so that, given the same initial information, different investigators would obtain the same results?By cladistic relationships we mean the evolutionary branching sequences among taxonomic units without regard to phenetic similarities among them or to an absolute time scale.There is no question that phylogenies could probably be reconstructed without error for any taxonomic group if complete fossil sequences for that group were available.However, can cladistic reconstructions be carried out with any degree of 1 This paper was presented on December 29, 1964, at a symposium entitled "Interactions between numerical and orthodox taxonomies" at Knoxville, Tennessee, before the Society of Systematic Zoology.2 Contribution No.