| Summary: | Paper I. Scale-worms are segmented worms. They can be found in all marine benthic habitats, including about 1200 species and over 200 genera. There has been little known about the phylogeny of this group and this study is aiming at achieving one. 56 terminal taxa are examined, including 8 outgroup taxa. Nuclear markers (18SrRNA, 28SrRNA) and mitochondrial markers (16SrRNA, COI) for the molecular analysis and 24 morphological characters were combined in the analysis. The data are analyzed with Bayesian analyses, maximum likelihood and parsimony. The combined data confirm that scaleworms is a monophyletic group. However, the scale-less pisionids and Palmyra aurifera Savigny in Lamarck, 1818, also nest within the scale-worms. In pisionids the lack of elytra represent a secondary loss but the case with P. aurifera is unresolved. There are multiple equally parsimonious pathways one can use to explain this. Only with the case of loss of elytra in P. aurifera, the scales represent a clear-cut synapomorphy (a shared derived state) for scaleworms. The phylogenetic result render some taxonomic changes on family and sub-family level. Paper II. More taxonomy is dealt with in a re-description of Bylgides sarsi (Kinberg in Malmgren, 1865) based on syntypes and fresh material from the Baltic Sea and the use of the phylogenetic results from the phylogeny discussed above. Paper III. Harmothoe imbricata (Linnaeus, 1767), has been reported as a colour-polymorphic species. Hitherto no genetic studies have confirmed this assumption leaving a possibility of cryptic species. 57 individuals representing 10 different colour morphs from Svalbard, Norway and Sweden were investigated. Based on two molecular markers it turns out that H. imbricata indeed is polymorphic and the only differences in allele frequencies is explained by distance. Paper IV. In systematics it is vital to have vouchers. Vouchers enable others to examine the taxonomic identity assigned to a sample by the author of a study. Vouchers are specimens, tissues or ...
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