Ultrastructural and immunohistochemical studies of the ontogeny of the nervous system and the mesoderm in Enteropneusta and Pterobranchia in order to elucidate deuterostome evolution.
Final Report Abstract
Deuterostomia is one of the major monophyletic groups in the animal kingdom. Interest in deuterostome evolution stems from the diversity of life cycles and anatomies present in this group and moreover from the fact that vertebrates are part of Deuterostomia. Phylogeny is a prerequisite for the understanding of evolution. I critically assess our current understanding of deuterostome phylogeny based on molecular and morphological data. Conflict in phylogenetic signal in molecular phylogenies is revealed utilizing data display networks and split analyses. Phylogenetic argumentation supports the hypothesis that the fossil "Pikaia gracilens" is a member of the stem lineage of Craniata. A first experimental data matrix based on "evo-devo" characters is presented and it is demonstrated that such a cladistics approach holds great potential for phylogenetic analysis of molecular developmental studies. The phylogenetic analysis of morphological characters is in conflict with several aspects of molecular phylogenies but more consistently explains the evolution of phenotypes based on a paradigm of descent with modification. An evolutionary scenario based on the phylogeny derived from the morphological data is presented.
