STRUCK, TORSTEN H*; WESTHEIDE, WILFRIED; PURSCHKE, G�NTER; Auburn University, AL; Universit�t Osnabr�ck, Germany; Universit�t Osnabr�ck, Germany: Origin of new species by sexual maturity in larval stages � Progenesis in polychaetes (Annelida)

The origin of species is among the most discussed, but least understood processes of biological evolution. One possible mechanism is progenetic evolution of small meiofaunal species. The resemblance of adult Dinophilidae and many Dorvilleidae to larval and juvenile stages of larger eunicid polychaetes suggests that they evolved progenetically within the Eunicida. Because the structures of larval and juvenile individuals belonging to different polychaete groups are more similar to one another than to the corresponding adults, the possibility of parallel progenetic evolution of similar larval and juvenile structures in different taxa cannot be excluded. Therefore, the phylogenetic affinity of Dinophilidae is uncertain. The position of the dorvilleids within the Eunicida has been substantiated by the homology of the jaw apparatus. Interestingly, dinophilids lack jaws. To infer the phylogeny of these taxa and determine if they have progenetic origins DNA-sequences (18S-rDNA, 28S-rDNA and CO I) of Dinophilidae, Dorvilleidae, other Eunicida, and other polychaetes, especially meiofaunal taxa, were determined. Prior to tree reconstruction detailed analyses of the alignments were conducted. Generalised parsimony and maximum likelihood methods were performed. On the one side closer relationships of assumed progenetic dorvilleids to large eunicidans is confirmed and on the other side the molecular data reject a sistergroup relationship of the Dinophilidae to any eunicidan taxa, thus indicating independent origin and convergent evolution of the different groups. Unfortunately, no other polychaete taxon can be significantly assigned as the sistergroup of the Dinophilidae; so their phylogenetic position remains unresolved.