A molecular phylogeny of annelids

Abstract

We present parsimony analyses of annelids based on the largest taxon sample and most extensive molecular data set yet assembled, with two nuclear ribosomal genes (18S rDNA and the D1 region of 28S rDNA), one nuclear protein coding-gene (Histone H3) and one mitochondrial ribosomal gene (16S rDNA) from 217 terminal taxa. Of these, 267 sequences are newly sequenced, and the remaining were obtained from GenBank. The included taxa are based on the criteria that the taxon must have 18S rDNA or at least two other loci. Our analyses show that 68% of annelid family ranked taxa represented by more than one taxon in our study are supported by a jackknife value > 50%. In spite of the size of our data set, the phylogenetic signal in the deepest part of the tree remains weak and the majority of the currently recognized major polychaete clades (except Amphinomida and Aphroditiformia) could not be recovered. Terbelliformia is monophyletic (with the exclusion of Pectinariidae, for which only 18S data were available), whereas members of taxa such as Phyllodocida, Cirratuliformia, Sabellida and Scolecida are scattered over the trees. Clitellata is monophyletic, although Dinophilidae should possibly be included, and Clitellata has a sister group within the polychaetes. One major problem is the current lack of knowledge on the closest relatives to annelids and the position of the annelid root. We suggest that the poor resolution in the basal parts of the trees presented here may be due to lack of signal connected to incomplete data sets both in terms of terminal and gene sampling, rapid radiation events and ⁄ or uneven evolutionary rates and longbranch attraction.

Multiple origins of pelagicism within Flabelligeridae (Annelida)

“…The species used here differs from the description of F. vitjasi by having two pairs of gonopores located at the anterior margins of the fourth and fifth chaetigers instead of the single pair reported by Buzhinskaya (1977 Struck et al (2007), Rousset et al (2007), and morphology (frontal palps, prostomium on top of peristomium, most with compound neurochaetae, epidermal papillae, and large (gonadal) papillae on one to three chaetigers of the anterior eight; Banse, 1969;Rouse and Pleijel, 2001;. Only vouchered and non-redundant (specimens collected from different localities) sequences available from GenBank were included in the analysis.…”

New primers reveal the presence of a duplicate histone H3 in the marine turtle leech Ozobranchus branchiatus

“…Reverse 1: H3R1 (5'-CCAACCAAGTACGCCTCA-3') Reverse 2: H3R2 (5'-CCAACCAAGTAAGCCTCG-3') H3R1 and H3R2 have an annealing temperature of 55ºC and functionally compatible with the H3af forward primer given in Rousset et al 2007.…”

“…in the marine turtle leech Ozobranchus branchiatus Nuclear protein coding-gene histone H3 were amplified using primers given in Rousset et al (2007). When multiple products were visible in the chromatograms for the histone H3 gene, new reverse primers synthesized by Invitrogen Corporation (Carlsbad, CA, USA) were employed to obtain better sequencing results (Lavretsky et al 2011 ):…”

Fossil clitellate annelid cocoons and their microbiological inclusions from the Eocene of Seymour Island, Antarctica

“…Their anatomical simplicity and the plasticity of key morphological characters of the body hinder precise taxonomic resolution of groups within extant Clitellata (Novo et al, 2011). Greatest taxonomic resolution has been achieved using molecular data (Apakupakul et al, 1999;Martin, 2001;Siddall et al, 2001;Erséus and Källersjö, 2004;Rousset et al, 2007;Marotta et al, 2008;Struck et al, 2011;Weigert et al, 2014) and ultrastructural characters of spermatozoa (Jamieson and Rouse, 1989;Ferraguti and Erséus, 1999;Cardini and Ferraguti, 2004;Marotta and Ferraguti, 2009), although such data are not yet available for fossils, and the relationships inferred among some groups are still disputed.…”