Reconstructing the phylogeny of the Sipuncula |
| |
Authors: | Schulze Anja Cutler Edward B Giribet Gonzalo |
| |
Institution: | (1) Department of Invertebrate Zoology, Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA;(2) Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA;(3) Smithsonian Marine Station, 701 Seaway Drive, Fort Pierce, FL 34949, USA |
| |
Abstract: | Sipunculans are marine spiralian worms with possible close affinities to the Mollusca or Annelida. Currently 147 species,
17 genera, 6 families, 4 orders and 2 classes are recognized. In this paper we review sipunculan morphology, anatomy, paleontological
data and historical affiliations. We have conducted cladistic analyses for two data sets to elucidate the phylogenetic relationships
among sipunculan species. We first analyzed the relationships among the 45 species of Phascolosomatidea with representatives
of the Sipunculidea as outgroups, using 35 morphological characters. The resulting consensus tree has low resolution and branch
support is low for most branches. The second analysis was based on DNA sequence data from two nuclear ribosomal genes (18S
rRNA and 28S rRNA) and one nuclear protein-coding gene, histone H3. Outgroups were chosen among representative spiralians.
In a third analysis, the molecular data were combined with the morphological data. Data were analyzed using parsimony as the
optimality criterion and branch support evaluated with jackknifing and Bremer support values. Branch support for outgroup
relationships is low but the monophyly of the Sipuncula is well supported. Within Sipuncula, the monophyly of the two major
groups, Phascolosomatidea and Sipunculidea is not confirmed. Of the currently recognized families, only Themistidae appears
monophyletic. The Aspidosiphonidae, Phascolosomatidae and Golfingiidae would be monophyletic with some adjustments in their
definition. The Sipunculidae is clearly polyphyletic, with Sipunculus nudus as the sister group to the remaining Sipuncula, Siphonosoma cumanense the sister group to a clade containing Siphonosoma vastumand the Phascolosomatidea, and Phascolopsis gouldi grouping within the Golfingiiformes, as suggested previously by some authors. Of the genera with multiple representatives,
only Phascolosoma and Themiste are monophyletic as currently defined. We are aiming to expand our current dataset with more species in our molecular database
and more detailed morphological studies. |
| |
Keywords: | Sipuncula phylogeny 18S rRNA 28S rRNA histone H3 Spiralia cladistic analysis |
本文献已被 SpringerLink 等数据库收录! |
|