A phylogenetic hypothesis for species of the genus Taenia (Eucestoda : Taeniidae)

Cladistic analysis of a numerical data matrix describing 27 characters for species of Taenia resulted in 4 most parsimonious phylogenetic trees (174 s teps; consistency index = 0.28; homoplasy index = 0.72; retention index = 0 .48). Monophyly for Taenia is diagnosed by the metacestode that is either a cysticercus or a form derived from a bladder-like larva; no other unequivo cal synapomorphies are evident. Tree structure provides no support for reco gnition of a diversity of tribes or genera within the Taeniinae: Fimbriotae niini and Taeniini have no phylogenetic basis. Hydatigera, Fimbriotaenia, F ossor, Monordotaenia. Multiceps, Taeniarhynchus, Tetratirotaenia must be su bsumed within Taenia as synonyms. Taenia saginata and Taenia asiatica are s ister species and distantly related to Taenia solium. Cospeciation with res pect to carnivorous definitive hosts and Taenia appears to be limited. Alth ough felids are putative ancestral hosts, contemporary associations appear to have resulted from extensive host-switching among felids, canids, hyaeni ds, and others. In contrast, relationships with herbivorous intermediate ho sts are indicative of more pervasive coevolution; rodents as intermediate h osts are postulated as ancestral for the Taeniidae, Taenia + Echinococcus. Patterns appear consistent with rapid shifts between phylogenetically unrel ated carnivores but among those that historically exploited a common prey r esource within communities in specific biogeographic regions.