Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 4, 1997
Publication Date: N/A
Interpretive Summary: Parasitism by tapeworms remains a considerable threat in agricul- ture (e.g. potential production losses in cattle and other ruminants), aquaculture (larval parasites in fishes), and as risk to human health. Efforts to limit the impact of tapeworms are dependent on our abilities to understand parasite biology, distribution and their potential as pathogens. Vital information is gained from the study and definition of phylogenetic relationships for these organisms, which leads to the development of predictive classifications. Studies in systematics provide the basic knowledge on distribution and relationships of host and parasitic organisms. Results from the present study provide the most robust hypothesis to date for the relatonships of major lineages of the tapeworms. Application of this information will influence ongoing research on the cyclophyllidean, proteocephalidean, and psuedophyllidean tapeworms that are significant pathogens in ruminant, piscine and human hosts.
The phylogeny of the Eucestoda was evaluated based on a suite of 46 binary and multistate characters derived from comparative morpho- logical and ontogenetic studies; attributes of adult and larval tapeworms were considered. A single most parsimonious tree (Cl= .868; Rl- .883; Hl= .535) was resolved fully dichotomous and is specified by the following; ((Gyrocotylidea, (Amphilinidea, ((Spathebothriidea, (Psuedophyllidea, ((Diphyllidea, (Trypanothyncha, (Tetraphyllidea, (Lecanicephalidea, ((Nippotaeniidea, (Tetrabothriidea, Cyclophyllidea)), Proteocephalidea))))), Haplobothriidea))), Caryophylidea))). Monophyly for the Eucestoda was firmly corroborated. Trees derived from the primary and Bootstrap analyses were congruent, but low values, particularly for relationships among the higher tapeworms indicated additional examination is warranted. This tree was found to be the most efficient hypothesis for describing character evolution and in specifying relationships among the orders when compared to those concepts that had been developed for the tapeworms over the past century. Areas of congruence shared among the current hypothesis and one or more of the prior hypotheses included: 1) Caryophyllids are basal and monozooy is ancestral; 2) Difossate forms are relatively primitive, and the Pseudophyllidea are the sister-group of the strongly polyzooic tapeworms; 3) The current study constitutes a complete historical review and poses a new and robust hypothesis for the phylogeny of the Eucestoda.