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Progenesis in Eunicida ("Polychaeta," Annelida)--separate evolutionary events? Evidence from molecular data.
Torsten H Struck1, Wilfried Westheide, Günter Purschke
1Spezielle Zoologie, Fachbereich Biologie, Universität Osnabrück, Barbarastrasse 11, D-49069 Osnabrück, Germany. struck@biologie.uni-osnabrueck.de
Molecular Phylogenetics and Evolution
|October 18, 2002
Summary
Phylogenetic analysis of annelids suggests separate evolutionary events for progenetic species within the Eunicida (segmented worms). Molecular data indicate the Dorvilleidae family is polyphyletic, challenging previous classifications.
Area of Science:
- Marine Biology
- Evolutionary Biology
- Annelid Taxonomy
Background:
- The Eunicida, a well-defined annelid taxon, includes families like Dorvilleidae, Lumbrineridae, Eunicidae, Onuphidae, and Hartmanniellidae.
- Certain Dorvilleidae species exhibit small size and simple organization, resembling larval forms, leading to the hypothesis of evolution via progenesis.
- The inclusion of Dinophilidae in this group is debated, with potential for parallel evolution of progenetic taxa.
Purpose of the Study:
- To infer the phylogeny of Eunicida, including Dinophilidae and progenetic dorvilleids.
- To investigate the evolutionary relationships within the Eunicida and the potential monophyly of related groups.
- To test the hypothesis of separate progenetic evolutionary events versus a single origin.
Main Methods:
- Determination of 18S ribosomal DNA (rDNA) sequences from various Dinophilidae, Dorvilleidae, and other Eunicida members.
- Data matrix expansion with sequences from annelid and molluscan species.
- Phylogenetic analysis using maximum parsimony, distance, and maximum likelihood algorithms with bootstrap support.
Main Results:
- Monophyly of Dinophilidae is highly supported.
- A clade enclosing Eunicidae and Onuphidae is strongly supported.
- A dorvilleid group, including the presumed progenetic *Parapodrilus psammophilus*, is monophyletic.
- The phylogenetic position of Dinophilidae within Eunicida remains unresolved.
- Molecular data suggest the Dorvilleidae family is polyphyletic.
- Tests rejected a constrained monophyly of Dinophilidae and *P. psammophilus*, supporting separate progenetic events.
Conclusions:
- The study supports separate progenetic evolutionary events rather than a single origin for progenetic taxa within Eunicida.
- The polyphyletic nature of Dorvilleidae indicates a need for re-evaluation of this annelid family.
- The precise phylogenetic placement of Dinophilidae within or outside Eunicida requires further investigation.