Abstracts - Deutsche Zoologische Gesellschaft

Zoological Systematics Symposium 93O ZS.1 (Sa) - ENNew insights into the phylogeny of the Opisthobranchia (Mollusca, Gastropoda) withspecial focus on critical groupsKatrin Göbbeler, Annette Klussmann-KolbPhylogenie and Systematics, Institute for Ecology, Evolution and Diversity, Johann WolfgangGoethe-Universität, Frankfurt a.M.The Opisthobranchia comprise morphologically very diverse gastropod species occurring worldwidein marine habitats. The phylogeny of the Opisthobranchia is controversially debated, sincedifferent studies yielded varying results. It is widely accepted that the Opisthobranchia encompassnine subgroups: Nudibranchia, Pleurobranchoidea, Acteonoidea, Cephalaspidea, Anaspidea, Pteropoda,Tylodinoidea, Acochlidiacea and Sacoglossa. The interrelationships of these subgroups areless clarified. Some sistergroup relationships like the one of Nudibranchia and Pleurobranchoidea(forming the taxon Nudipleura) constantly occur in various analyses. But the position of some othersubgroups especially of Acteonoidea, Tylodinoidea and Sacoglossa has proven to be highly variable.The purpose of the present study is to reinvestigate the phylogeny of the Opisthobranchia usingmolecular systematic methods. Special emphasis is given to “critical” groups, which are discussedin detail by also taking morphological characters into consideration. The dataset comprises taxa ofall opisthobranch subgroups, as well as further members of the Euthyneura, basal heterobranchs andcaenogastropods. Four different markers were used: the complete 18S rRNA, partial 28S rRNA,partial 16S rRNA and partial mitochondrial CO1 sequences. Phylogenetic reconstruction was performedusing Baysian inference approaches and maximum likelihood.O ZS.2 (Sa) - ENThe Heterobranchia (Mollusca, Gastropoda) – molecular phylogeny and evolutionAngela Dinapoli, Annette Klussmann-KolbPhylogeny and Systematics, Institute for Ecology, Evolution and Diversity, Johann WolfgangGoethe-Universität, Frankfurt a.M.The taxon Heterobranchia comprises the Euthyneura (with Opisthobranchia and Pulmonata) andseveral little-known “basal” groups. Evolutionary relationships among Heterobranchia especiallythe Euthyneura have been the subject of extensive controversy. The inclusion of “basal” taxa (e.g.Pyramidellidae, Architectonicidae, Rissoellidae, Omalogyridae) has been neglected in some morphologicaland most of the molecular studies. In the present study we inferred a phylogenetic hypothesisby using a multi-gene dataset including nuclear and mitochondrial genes of the Heterobranchia.The taxon sampling includes representatives of many important “basal” heterobranch families withuncertain systematic affinities (e. g. Larochella, Graphis), and additional members of several groupsthat have been poorly represented in earlier morphological and molecular investigations (e. g. Omalogyra,Rissoella). An a priory examination of the phylogenetic signal of molecular data was carriedout with split decomposition methods (SplitsTree) and phylogenetic trees were reconstructed usingmaximum parsimony (PAUP), maximum likelihood (RAxML) and Bayesian methodologies (Mr-Bayes). Our recent molecular phylogenetic work provides the most comprehensive molecular studyof Heterobranchia relationships to date and supplies new insights into the evolution and phylogenyof this enigmatic taxon.