Complete genome sequences of four novel mycobacteriophages, Diminimus, Dulcita, Glaske16, and Koreni, isolated from soil are presented. All these bacteriophages belong to subcluster M1, except Koreni ...that belongs to subcluster A4. Moreover, all have siphovirus morphologies, with genome sizes ranging from 51,055 to 81,156 bp.
The spatial distribution of the muddy fine sand community from the Bay of Veys (western English Channel) were investigated during spring and autumn 1997. A grid of 55 and 54 sites was sampled in ...March and October, respectively, using two replicates per site of a Hamon grab (0.25 m
2) for macrofauna collection and an additional one for sediment analysis. A total of 172 species were sampled with a dominance of polychaetes, followed by crustaceans and bivalves. The species richness and abundance show low temporal changes despite higher values in October than in March. In March, the mean abundance was 165 ind. 0.5 m
−2; in October, the mean abundance was 212 ind. 0.5 m
−2. Four assemblages from the
Abra alba–
Pectinaria koreni community were identified corresponding to a bathymetric and sedimentary gradient from muddy fine sands with high levels of fine particles in shallow water to fine sands in deeper water. The discussion focuses on factors prevailing on the spatial structure of sandy communities in the English Channel.
The North Atlantic intertidal gastropod, Littorina saxatilis (Olivi, 1792), exhibits extreme morphological variation between and within geographic regions and has become a model for studies of local ...adaptation; yet a comprehensive analysis of the species' phylogeography is lacking. Here, we examine phylogeographic patterns of the species' populations in the North Atlantic and one remote Mediterranean population using sequence variation in a fragment of the mitochondrial cytochrome b gene (607 bp). We found that, as opposed to many other rocky intertidal species, L. saxatilis has likely had a long and continuous history in the Northwest Atlantic, including survival during the last glacial maximum (LGM), possibly in two refugia. In the Northeast Atlantic, several areas likely harboured refugial populations that recolonized different parts of this region after glacial retreat, resulting in strong population structure. However, the outlying monomorphic Venetian population is likely a recent anthropogenic introduction from northern Europe and not a remnant of an earlier wider distribution in the Mediterranean Sea. Overall, our detailed phylogeography of L. saxatilis adds an important piece to the understanding of Pleistocene history in North Atlantic marine biota as well as being the first study to describe the species' evolutionary history in its natural range. The latter contribution is noteworthy because the snail has recently become an important model species for understanding evolutionary processes of speciation; thus our work provides integral information for such endeavours.
The influence of three different species of tubicolous worms (Pygospio elegans, Polydora ciliata and Lagis koreni) on the hydrodynamic bottom roughness length (z sub(0)) was analysed in this study. ...Flume experiments and geospatial methods were combined to determine the potential interactions between worm tubes and the near-bed flow regime and the resulting effects on sediment transport in the south-western Baltic Sea. The three selected species are common in the area of interest (3539 km super(2)). Their species-specific population densities were taken from existing macrozoobenthos datasets and transferred into a Geographic Information System (GIS). In analogy to the sediment roughness length, the hydrodynamic roughness lengths generated by the tubicolous worms were calculated and corresponding sediment transport values, derived from flume experiments with artificial tube lawns, were geospatially analysed using GIS. In order to show the direct influence of worm tubes on the surrounding sediment surface flume experiments were conducted at two given current velocities of 20 cm s super(-) super(1) for sediment displacement effects and 5 cm s super(-) super(1) for deposition effects. The roughness length was shown to increase by a factor of 2 to 30 in the presence of biogenic structures such as the worm tubes. The near-bed hydrodynamic conditions are significantly influenced at low roughness densities through independent or isolated flow conditions at 0.7 to 1.9% and at high roughness densities between 4.2 and 7.5%, resulting in unaffected sediment surfaces through ''skimming flow'', as well. The GIS analysis revealed that this effect occurs over 4% (137 km super(2)) of the area of investigation, whereas sediment displacement at roughness densities between 0.7 and 1.9% due to increased turbulence is the predominant effect over 33% (present on 1172 km super(2)) of the area of investigation. These findings reveal the important influence of species-generated microtopography on sediment transport processes.
The historic processes which have led to the present‐day patterns of genetic structure in the marine coastal fauna of the Northeast Atlantic are still poorly understood. While tectonic uplifts and ...changes in sea level may have caused large‐scale vicariance, warmer conditions during glacial maxima may have allowed pockets of diversity to persist to a much wider extent than in the Northwestern Atlantic. The large‐scale geographic distribution of deeply divergent lineages of the coastal polychaete tubeworms Pectinaria koreni (two clades) and Owenia fusiformis (three clades) were compared using a fragment of the mitochondrial cytochrome oxidase I gene (mtCOI). All lineages were present along the biogeographic transition zone on the north coast of Brittany (France) and we found evidence pointing towards congruence in the timing of cladogenic events between Pectinaria sp. (P. auricoma/P. belgica and P. koreni) and Owenia sp., suggesting a shared history of vicariant events. More conserved 16SrRNA sequences obtained from four species of Pectinariidae together with mtCOI sequences of P. koreni seem consistent with an initial establishment of pectinariids in the north, and a southward colonization of the Northeast Atlantic. Phylogeographic patterns in O. fusiformis were also consistent with a north/south pattern of lineage splitting and congruent levels of divergence were detected between lineages of both species. We observed signatures of both persistence in small northern glacial refugia, and of northwards range expansion from regions situated closer to the Mediterranean. However, whether the recolonization of the Northeast Atlantic by both species actually reflects separate interglacial periods is unclear with regards to the lack of molecular clock calibration in coastal polychaete species.
The polychaete Pectinaria koreni exhibits a complex life cycle characterized by non-overlapping generations and widespread larval dispersal. To explore how “local” metapopulation genetic structure ...varies spatially and temporally during population turnover, we combined observations on demography, larval dispersal through hydrodynamic modelling and population genetics of successive age cohorts in the Baie de Seine (eastern English Channel, France). Mature adults (March), newly settled (July) and later-stage juveniles (September) were sampled in 2003 on the edge and in the main demes of the metapopulation. Demes displayed an asynchronous dynamics due to variations in habitat quality affecting reproductive timing (e.g. three distinct spawning events observed) and in local larval supply linked to temporal fluctuations of hydrodynamism. Two-source populations were identified among dense areas with the greatest larval retention and self-recruitment rates: one with a single recruitment event, stable temporal genetic variation and a strong spatial genetic re-homogenization during turnover, and the other with two recruitment events and significant allele frequency changes over time. Sink habitats displayed single recruitment event and experienced strong inter-generational (juveniles vs adults) genetic changes due to genetic drift associated with strong winter mortalities. Altogether, results suggested that adult spawning asynchrony and sweepstakes reproductive success, together with genetic drift, played a greater role than hydrodynamics itself in determining effective recruitment rates at some sites and generating genetic patchiness.
The relationship between meroplankton distribution and spatio-temporal variability of coastal mesoscale hydrological structure was investigated in the northern Bay of Biscay, North-East Atlantic. For ...the three coastal polychaetes studied, i.e. Pectinaria koreni, Owenia fusiformis and Sabellaria alveolata, the highest larval abundances were sampled in low-salinity, low-density and high-temperature river plume waters. For two species (P. koreni and O. fusiformis), maximal abundances were observed in the surface and thermocline layers due to ontogenic migrations. Variance partitioning based on multiple regression and redundancy analyses was used to assess the relative roles played by the hydrological environment alone, the geographical space alone and their interactions, i.e. the spatial structure of the hydrological environment. These analyses demonstrate the key role played by the hydrological spatial structure in the distribution of larval abundances. The hydrological environment alone was insignificant, whereas geographical space alone explained a significant part of the variability in meroplankton distribution, probably in conjunction with ecological processes. For species whose benthic populations are spatially structured, the distribution and the size of adult populations and the timing of spawning events can significantly affect larval distribution and dispersal.
This study uses enzymatic and mitochondrial genes to infer the relative importance of historical processes and contemporary hydrodynamic features on the observed patterns of genetic structure in ...subdivided populations of Pectinaria koreni (Polychaeta: Pectinariidae) along the coasts of Brittany and the English Channel. Nucleotide sequence variation of a 603-bp fragment of the mtDNA cytochrome oxidase subunit I gene revealed a surprisingly deep phylogeographic break of about 16% divergence separating the Brittany and Channel populations, which coincides with a biogeographic boundary along the western coast of Brittany. Deep sequence divergence with fixed haplotype differences and the inversion of allele frequencies at two enzyme loci suggests the occurrence of potential cryptic or sibling species of P. koreni. The two clades showed opposite features. Channel populations exhibited bimodal match-mismatch curves due to two highly divergent haplotypes occurring at high frequencies and no overall heterozygote deficiencies at enzyme loci, suggesting respectively, a historic secondary contact between two differentiated populations followed by contemporary panmixia. On the contrary, Brittany populations displayed unimodal curves with low nucleotide diversity and highly significant heterozygote deficiencies, probably reminiscent of a recent population expansion and recolonisation of Brittany with contemporary admixture of divergent populations.
In a dispersive coastal area under multiple organic enrichment sources, stable isotopes were used to trace organic sources of carbon and nitrogen in sediments and benthic macrofauna. The Bivalve Abra ...alba and the Polychaetes Nephtys sp. and Pectinaria (Lagis) koreni were reliable indicators of the input of terrestrial-derived organic matter into this coastal area, either originated in outfall sewage discharges or estuarine outflow. An isotopic depletion was observed up to 250m from the outfall branches, much stronger in the biota than in the sediments. An enrichment of 2‰ in the sediments, and 2–6‰ in the species was noticed in sites located farther than 1500m from the outfall. Depositivores and carnivores/omnivores gave the best picture of the extension of the sewage dispersion and incorporation into the food web.
PDF
