Phylogeny of scale-worms (Aphroditiformia, Annelida), assessed from 18SrRNA, 28SrRNA, 16SrRNA, mitochondrial cytochrome c oxidase subunit I (COI), and morphology.

The phylogeny of scale-worms, benthic polychaetes carrying dorsal scales (elytra), including taxa from Acoetidae, Aphroditidae, Eulepethidae, Pholoidae, Pholoididae, Polynoidae and Sigalionidae (Aphroditiformia), is assessed from the nuclear markers 18SrRNA and 28SrRNA, and mitochondrial 16SrRNA and cytochrome c oxidase subunit I (COI), and 24 morphological characters. The data sets are analyzed both separately and combined, with Bayesian analyses, maximum likelihood and parsimony. In total, 56 terminal taxa are examined, including 48 taxa from all scale-worm families, and eight out-group species. The results indicate that Aphroditidae and Eulepethidae are the most basally placed families among the scale-worms. The Pholoididae and Pisionidae are positioned within and synonymized with the Sigalionidae, and Pholoidae may be part of the same group. The subfamily Iphioninae falls out as sister group to a clade consisting of Polynoidae and Acoetidae and is elevated to Iphionidae. The families now included in the Aphroditiformia are Acoetidae, Aphroditidae, Eulepethidae, Pholoidae, Polynoidae, Iphionidae and Sigalionidae, and the subfamily name Harmothoinae and Acholoinae are treated as a junior synonyms of Polynoinae.

Environmental correlates of population differentiation in Atlantic herring.

The marine environment is characterized by few physical barriers, and pelagic fishes commonly show high migratory potential and low, albeit in some cases statistically significant, levels of genetic divergence in neutral genetic marker analyses. However, it is not clear whether low levels of differentiation reflect spatially separated populations experiencing gene flow or shallow population histories coupled with limited random genetic drift in large, demographically isolated populations undergoing independent evolutionary processes. Using information for nine microsatellite loci in a total of 1951 fish, we analyzed genetic differentiation among Atlantic herring from eleven spawning locations distributed along a longitudinal gradient from the North Sea to the Western Baltic. Overall genetic differentiation was low (theta = 0.008) but statistically significant. The area is characterized by a dramatic shift in hydrography from the highly saline and temperature stable North Sea to the brackish Baltic Sea, where temperatures show high annual variation. We used two different methods, a novel computational geometric approach and partial Mantel correlation analysis coupled with detailed environmental information from spawning locations to show that patterns of reproductive isolation covaried with salinity differences among spawning locations, independent of their geographical distance. We show that reproductive isolation can be maintained in marine fish populations exhibiting substantial mixing during larval and adult life stages. Analyses incorporating genetic, spatial, and environmental parameters indicated that isolating mechanisms are associated with the specific salinity conditions on spawning locations.