Phylogenetic analysis of the higher classification of the Nematoda

Abstract

Inglis (W. G. Inglis. 1983. Aust. J. Zool. 31: 243–255) divided Nematoda into three classes: the Enoplea, Rhabditea, and Chromadorea. Although most nematologists agree as to the limits of each of these groups, there is much disagreement as to how the groups relate to one another. Some authors group the Chromadorea with the Rhabditea, others group the Chromadorea with the Enoplea, and still others treat the three as independently derived taxa. In the present study I examine characters upon which various versions of the classification are based to identify plesiomorphic and derived character states. These are used to construct a phylogenetic tree using the Wagner algorithm. The analysis suggests that the Enoplea are best treated as the sister group to the Chromadorea–Rhabditea. The Chromadorea appear to be paraphyletic, consisting of several lineages forming a grade between the Enoplea and Rhabditea.