Phylogeny of sipunculan worms: A combined analysis of four gene regions and morphology

Re-evaluating the phylogeny of Sipuncula through transcriptomics

“…As with previous molecular hypotheses (e.g., Maxmen et al, 2003;Schulze et al, 2007;Kawauchi et al, 2012) our transcriptome analyses confirm Sipunculidae as the sister clade to all other sipunculans. Development through a planktotrophic pelagosphera larva, unique among all metazoan larval types, is the only life history pattern observed thus far in Sipunculidae (Hatschek, 1883;Rice, 1988), suggesting planktotrophy as the plesiomorphic pattern of development within Sipuncula (Cutler, 1994).…”

“…Outside Golfingiidae, transcriptome analyses also recovered a distinct position for Siphonosoma (Siphonosomatidae), consistent with one of the new familial assignments proposed by Kawauchi et al (2012). A distinct branch indicating the possibility of 'Siphonosomatidae' was also recovered in previous molecular hypotheses, which show alternative branching patterns, although this taxon was not formally named (Maxmen et al, 2003;Schulze et al, 2007). In all cases Siphonosoma was repositioned outside Sipunculidae, where it had been placed in an earlier classification scheme by parsimony analyses of morphological characters (Cutler and Gibbs, 1985).…”

“…For little more than a decade, attempts to resolve sipunculan relationships primarily utilized a small number of candidate genes from a common list of species (Maxmen et al, 2003;Staton, 2003;Schulze et al, 2005Schulze et al, , 2007Kawauchi et al, 2012). Our study represents the first use of entirely new sequence data, and a methodological departure from those earlier studies.…”

“…observation (Rice, 1970), planktotrophy is also the exclusive life history pattern in all other families (Siphonosomatidae, Aspidosiphonidae, Phascolosomatidae and Antillesomatidae) with one exception; Golfingiidae is the only clade in which all four life history patterns have been observed, and where the broadest diversity of larval and adult forms have been described (Rice, 1985;Pilger, 1987;Schulze et al, 2007;Schulze and Rice, 2009b;Kawauchi et al, 2012). Therefore, answers to fundamental questions about larval development, dispersal, speciation, and patterns of biodiversity may be found within this most genera-rich family.…”

“…Efforts to identify and name sipunculan families have progressed for more than a century, beginning with the use of several non-distinct group names (Baird, 1868;Pickford, 1947;Åkesson, 1958), followed by the establishment of four distinct families, Sipunculidae, Golfingiidae, Phascolosomatidae and Aspidosiphonidae (Stephen and Edmonds, 1972), and an increase to six families with the addition of Themistidae and Phascolionidae (Cutler and Gibbs, 1985). Over the past three decades, internal relationships within and among sipunculan clades have been inferred through numerical analyses of taxonomic characters (Cutler and Gibbs, 1985), DNA sequence data (Maxmen et al, 2003;Staton, 2003), and the combined use of morphological and molecular characters (Schulze et al, 2005(Schulze et al, , 2007. More recently, an extended dataset of six gene loci was analysed, building upon previous molecular approaches, and proposing a revised classification system with the following six sipunculan families: Sipunculidae, Golfingiidae, Siphonosomatidae, Antillesomatidae, Phascolosomatidae and Aspidosiphonidae .…”