ONTOGENETIC SEQUENCES AND THE PHYLOGENETICS OF PARASITIC FLATWORM LIFE CYCLES.

Abstract- Ontogenetic data can be used in phylogenetic analyses (1) as tests of character homology, (2) for polarizing transformation series, and (3) as characters themselves. The ontogenetic sequence of semaphoronts can change by addition, substitution, or deletion of stages which are either terminal or nonterminal. Outgroup comparisons can use life cycle data as well as morphological data to establish a general reference system of inferred genealogy, which can then be used to distinguish which of the six ontogenetic sequence changes has occurred in a particular phylogeny.