First global phylogeny of a deep-sea group of molluscs
Exploring deep-sea biodiversity across the World
This work is part of the PhD of Justine Siegwald based at the Department of Natural History, University Museum of Bergen (UiB) and results from a cooperation with Dr Trond Oskars a previous PhD at the University Museum and Prof. Yasunori Kano from the University of Tokyo, Japan.
It representes the most comprehensive phylogeny of a globally distributed deep-sea group of gastropods published to date including over 80% of the recognized diversity of the family Scaphandridae. The definition and taxonomic composition of the Scaphandridae has been hampered by the lack of a sound phylogenetic framework and definition of synapomorphic traits. In this work it was used a combination of molecular phylogenetics (Bayesian Inference and Maximum Likelihood) based on five gene markers (cytochrome c oxidase subunit I, 12S rRNA, 16S rRNA, 18S rRNA, and 28S rRNA) and morpho-anatomical characters to redefine the Scaphandridae and its genera. A new classification is proposed with the three genera Nipponoscaphander, Sabatia, and Scaphander. The main differences between genera lie on the shells (shape, parietal callus, spire) and male reproductive system (prostate). The species Hamineobulla kawamurai is reassigned to the closely related family Eoscaphandridae, currently defined mostly based on pleisiomorphic traits. Biogeographically the genus Nipponoscaphander was found to be restricted to the Indo-West Pacific; Sabatia is mostly circumscribed to the Indo-West Pacific, but has one lineage present in the north Atlantic Ocean. Polyphyly across ocean realms prevails in the specious and globally distributed genus Scaphander with multiple speciation events between Indo-Pacific and Atlantic lineages but also with several episodes of cladogenesis within realms. Two rare cases of species with a broad distribution spanning the Indo-West Pacific and Atlantic realms are confirmed (S. meridionalis and S. nobilis).