Holistic Pattern Analysis as an Alternative to Pattern Cladistics in Hypothesizing Crustacean Phylogenetic Sequences

Abstract

There has been a growing realization that ‘true’ phylogenetic relationships cannot be determined using pattern cladistical methods alone. The applications of such techniques to the problem of crustacean evolution is first examined using the results presented by Wilson (in this issue). It is found that the degree of correlation of characters in the head vs trunk regions explains very well the grouping of taxa in the cladograms, suggesting that the groups are nothing more than mathematical constructs. The argument is presented that functions of different parts of the crustacean body need to be determined, along with an understanding of how the body morphology is designed in accordance with the dominant functions. A method for producing hypothesized phylogenetic sequences from an analysis of body morphology is proposed and examined using the amphipod family Iphimediidae. It is suggested that cladograms are merely hypotheses and can be tested using functional morphological information of the type outlined.