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Phylogenetic Systematics and Evolution

Tree of life: higher phylogeny of molluscs

Phylogenetic Relationships of the Cephalaspidea

Cephalaspidea are an Order of Gastropoda with an estimated 840 marine living species worldwide, largely bearing an external shell. They are of special evolutionary interest because traditionally the group has been considered the most basal offshoot of the Opisthobranchia, but this phylogenetic position is nowadays disputed. Moreover the validity and definition of most families (ca. 21) and genera (ca. 73) is not well established and their relationships are poorly known. This results, somehow, from inadequate descriptions in some cases based on shells alone or few anatomical characters, which seem to be too variable for phylogenetic inference.

This project aims to achieve a complete family-level phylogeny of the Cephalaspidea inferred from molecular sequences of mitochondrial and nuclear genes. The goals are to investigate the monophyly of families and their phylogenetic relationships and shed light on the overall systematics of the group.

Principal investigator: Manuel Malaquias (Bergen Museum). Collaborators: Philippe Bouchet (Paris’s Natural History Museum) and Terry Gosliner (California Academy of Sciences.)

 

The Phylogeny of Haminoeidae

Haminoeidae gastropods are the most genera-rich family in the Order Cephalaspidea with 40 extant genera described. Haminoids are bubble-shelled marine snails inhabiting mostly soft sediments of sandy-mud sometimes with seagrass or algae. Most generic diversity results from shell based studies alone but shell characters such as overall shape, striation, columelar callus, etc., are probably not diagnostic at the generic level. This resulted in a poorly defined taxonomy and validity of most genera is uncertain.

This project aims to produce a comprehensive molecular phylogeny of the family and to reconcile molecular, anatomical, and shell data in order to test the classical taxonomic arrangement of the group.

Principal investigator: Manuel Malaquias (Bergen Museum). Collaborators: Clay Carlson (Guam) and Paula Mikkelsen (Institute of Paleontology, New York).

 

Phylogeny of Caudofoveata

The worm-like, shell-less aplacophoran molluscs (Caudofoveata = Chaetodermomorpha and Solenogastres = Neomeniomorpha) have recently received much attention due to the fact that they are considered basal among the Mollusca. The Caudofoveata, also known as Chaetodermomorpha, is by far the least known class of molluscs. Not the least these basal molluscs are important for our understanding of the evolution of the Mollusca, and also for our understanding of the evolution of the Bilateria from the Cambrian and onwards. The internal relationships of the taxon, however, are not known, and the evolutionary relationships of the group have never been tested in a proper phylogenetic analysis, neither based on morphological or molecular data. Caudofoveates are common in Scandinavian waters, but commonly misidentified and many species remain undescribed. The aims of the project are to identify and describe all species of caudofoveates from Norwegian waters and to construct a solid hypothesis for the phylogeny of the Caudofoveata and for the placement of the group relative to other molluscs, using molecular and morphological methods.

Principal investigator: Nina Mikkelsen (Bergen Museum), Endre Willassen (Bergen Museum), Christoffer Schander (Department of Biology), Christiane Todt (Department of Biology).