Supervisor: Thomas Schwaha
PhD Defensio - Tuesday, February 17th 2026, 11:30 am CET
HS2, UBB, Djerassiplatz 11030 Vienna
Abstract
Bryozoans are colonial suspension-feeders in aquatic habitats, with the limnetic Phylactolaemata representing the earliest-branching clade. This thesis investigates the morphology and evolution of phylactolaemates by studying the little-investigated Lophopodidae as well as Hirosellidae and integrates new morphological data into the general character evolution of the clade. It complements previous observations of lophopodids, sheds new light onto their neuro-, myoanatomy and provides new apomorphies located in the lophophoral base. The phylogenetic position of Plumatella fruticosa is clarified via an integrative approach of molecular and morphological data. The new phylogeny places P. fruticosa outside Plumatellidae, closer to Fredericellidae as sister taxon to the morphologically distinct Cristatellidae and Pectinatellidae. Morphological characters on colony and zooid level support the exclusion of P. fruticosa from plumatellids and its closer association to fredericellids. The close relationship to Cristatellidae and Pectinatellidae, however, remains enigmatic. Altogether this resulted in establishment of the family Hirosellidae and the reclassification of Hirosella fruticosa. All previous morphological analyses and data of this thesis were compiled into a character matrix and mapped onto the newly erected molecular phylogeny. Ancestral state reconstruction suggests colonies with large interzooidal distances and non-encrusting cystids as ancestral. Phylactolaemates show a largely conserved neuro-/myoanatomy, although several lineage specific adaptations occur, some of which evolved convergently. Overall, this thesis refines the phylogeny of phylactolaemates and gives us a better understanding of their morphological evolution. The establishment of a new phylogeny, Hirosellidae and an extensive character matrix provides a good framework for future research, that should address functional and ecological aspects as well.
