Phylogenetic relationships within Serpulidae (Annelida: Polychaeta) inferred from molecular and morphological data.
We assessed phylogenetic relationships within Serpulidae (including Spirorbinae) using parsimony and Bayesian analyses of 18S rDNA, the D1 and D9-D10 regions of 28S rDNA, and 38 morphological characters. In total, 857 parsimony informative characters were used for 31 terminals; 29 serpulids and sabellid and sabellariid outgroups. Following ILD assessment the two sequence partitions and morphology were analyzed separately and in combination. The morphological parsimony analysis was congruent with the results of the earlier preliminary analysis by Kupriyanova (2003) in suggesting that a monophyletic Serpulinae and Spirorbinae respectively form a clade, while the remaining serpulids form a basal grade comprising what are normally regarded as Filograninae. Bremer support values were however quite low throughout. In contrast, the combined analyses of molecular and morphological data sets provided highly resolved and well-supported trees, though with some conflict when compared to the morphology-only analysis. Spirorbinae was recovered as a sister group to a monophyletic group composed of both ‘filogranin’ taxa (Salmacina, Filograna, Protis, and Protula) and ‘serpulin’ taxa such as Chitinopoma, Metavermilia, and Vermiliopsis. Thus the traditionally formulated sub-families Serpulinae and Filograninae are not monophyletic and this indicates that a major revision of serpulid taxonomy is needed at the more inclusive taxonomic levels. We refrain from doing so based on the present analyses since we feel that further taxon sampling and further molecular sequencing is required. The evolution of features such as the operculum and larval development are discussed.