MCHUGH, Damhnait: Molecular phylogenetic analyses indicate a rapid radiation of polychaete annelids

The phylogenetic relationships of terebellidan and sabellidan polychaete annelids were investigated using elongation factor-1alpha (EF-1alpha) sequences alone and in combination with previously published data for three other genes. Forty-three ingroup taxa were sampled, including representatives of the Terebellidae, Ampharetidae, Alvinellidae, Pectinariidae, Trichobranchidae, Flabelligeridae, Cirratulidae, Siboglinidae, Serpulidae, Sabellidae, Sabellariidae, Oweniidae, Arenicolidae, Capitellidae, Maldanidae, Chaetopteridae, and Spionidae; eunicids and onuphids were designated as the outgroups for the analyses. EF-1alpha sequences for these taxa were analyzed using maximum parsimony and maximum likelihood. Monophyly of the ingroup is supported by the analyses, as is monophyly of 12 of the ingroup taxa for which two or more representatives were included. The resultant topology also shows a terebellidan clade including Terebellidae, Ampharetidae, Alvinellidae, and Trichobranchidae, but not the Pectinariidae, which falls within a clade also containing Chaetopteridae, Spionidae, Cirratulidae and Flabelligeridae; this latter clade is sister to a Sabellidae-Serpulidae-Sabellariidae clade; the Oweniidae, Siboglinidae, Capitellidae, Maldanidae, and Arenicolidae together form the sister group to the terebellidan clade. However, support for these basal relationships is weak. For a more limited taxon sample, combined analyses of EF-1alpha, 28S rDNA, U2 snRNA and histone H3 was undertaken. Again, the support for monophyly of traditionally recognized �families� is strong, but is weak for the basal relationships among them. The lack of support for resolution of basal nodes even when several genes are analyzed suggests a rapid radiation of these annelids [Supported by NSF-DEB #9806848]