Cryptic speciation at organic‐rich marine habitats: a new bacteriovore annelid from whale‐fall and fish farms in the North‐East Atlantic

Vigtorniella ardabilia sp. nov. , a new chrysopetalid annelid, is described from a whale‐fall in Sweden and from sediment samples collected beneath fish farms in Norway. The new Vigtorniella species is morphologically almost identical to Vigtorniella flokati from whale‐falls in the Pacific Ocean, although molecular evidence from four genes shows that they are different species. Population genetic structure and phylogenetic relationships of V. ardabilia sp. nov. were assessed using molecular data from the nuclear genes 18S and 28S, and the mitochondrial 16S and cytochrome c oxidase subunit I (COI). High levels of gene flow are reported between contrasting organic‐rich environments in the North Atlantic (fish farms and whale‐fall). Observations of feeding biology and habitat suggest that V. ardabilia specializes on bacterial mats, rather than on whale‐falls, although the two species of Vigtorniella for which data were available show very different feeding behaviours. Our results further showed an unexpectedly low divergence rate in Vigtorniella for the mitochondrial markers, suggesting stabilizing selection. Analyses carried out with parsimony, maximum likelihood, and MrBayes all placed the genus Vigtorniella as sister group to Dysponetus, suggesting a close evolutionary link to sediment‐dwelling fauna. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 774–785.