Submitted to: Zoologica Scripta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 4, 2000
Publication Date: N/A
Interpretive Summary: Phylogenetic relationships among members of the phylum Platyhelminthes have received extensive scrutiny over the past 20 years. We report the results of the most complete analyses of the Neodermata, or largely parasitic flatworms, based on evaluation of morphological characters. The parasitic playthelminths represent one of the most extensively studied animal groups with a database assembled over the past 200 years that will soon exceed 2500 morphological characters. This represents historical continuity of our studies of flatworms, comprising a formidable assemblage of knowledge about structure and biology. Results of the current study indicate that comparative morphology remains viable, tractable and powerful. Phylogenetic analyses using morphological data provide an excellent framework for assessing our young but growing molecular database. Phylogenetic resolution for parasitic taxa contributes directly to a robust understanding of biochemical, physiological, and developmental pathways along with insights about life history patterns associated with parasitism. Phylogeny provides the foundation for elucidating novel approaches for the control of parasites, parasitism and disease.
Phylogenetic systematic analysis of 24 taxa representing the rhabdocoel platyhelminths , based on a suite of 90 morphological characters, produced a single fully resolved tree of 193 steps with a consistency index of 0.66. Bootstrap and jackknife analyses, however, indicated that only the following portion of the tree was tobust: (Kytorhynchidae (Promesostomidae ((Trigonosomidae + Kalyptorhynchidae) ((Typhloplanidae (Dalyellidae + Temnocephalida)) ((Fecamipidae + Urostoma) (Udonella ((Aspidobothrea + Digenea) (Monogenoidea((Gyrocotylidea (Amphilinidea + Eucestoda)))))))))). That portion of the tree has a CI of 0.78. The portion of the tree comprising the Neodermata, including Udonella as sister group of the (Trematoda + Cercomeromorphae), has a CI= 0.89. Previous disagreements among phylogenetic systematic analyses of these taxa have been due to the influence of missing data for critical characters in key taxa and differences in the taxa analyzed, rather than any inherent weakness of the morphological data set used to construct the hypotheses. Non-phylogenetic systematic approaches to homology assessment and misconceptions regarding phylogenetic systematic methodology are addressed.