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| 2. |
- Ruzzante, D. E., et al.
(författare)
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Biocomplexity in a highly migratory pelagic marine fish, Atlantic herring
- 2006
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Ingår i: Proceedings of the Royal Society B-Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 273:1593, s. 1459-1464
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Tidskriftsartikel (refereegranskat)abstract
- The existence of biologically differentiated populations has been credited with a major role in conferring sustainability and in buffering overall productivity of anadromous fish population complexes where evidence for spatial structure is uncontroversial. Here, we describe evidence of correlated genetic and life history (spawning season linked to spawning location) differentiation in an abundant and highly migratory pelagic fish, Atlantic herring, Clupea harengus, in the North Sea (NS) and adjacent areas. The existence of genetically and phenotypically diverse stocks in this region despite intense seasonal mixing strongly implicates natal homing in this species. Based on information from genetic markers and otolith morphology, we estimate the proportional contribution by NS, Skagerrak (SKG) and Kattegat and western Baltic (WBS) fish to mixed aggregations targeted by the NS fishery. We use these estimates to identify spatial and temporal differences in life history (migratory behaviour) and habitat use among genetically differentiated migratory populations that mix seasonally. Our study suggests the existence of more complex patterns of intraspecific diversity than was previously recognized. Sustainability may be compromised if such complex patterns are reduced through generalized management (e.g. area closures) that overlooks population differences in spatial use throughout the life cycle.
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| 3. |
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| 4. |
- Mariani, S., et al.
(författare)
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North Sea herring population structure revealed by microsatellite analysis
- 2005
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 303, s. 245-257
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Tidskriftsartikel (refereegranskat)abstract
- The Atlantic herring Clupea harengus has played a pivotal role in the formulation of ideas relating to population structuring in marine fishes, yet considerable uncertainty remains as to the extent to which phenotypic and genetic differentiation coincide in such a highly mobile species. In this study, we examined genetic population structure across the major herring spawning aggregations in the North Sea and adjacent waters over 2 years, 2002 and 2003. We analysed 1660 spawning individuals across 9 microsatellite loci. Data were analysed using several approaches, taking into account the effect of location, year-class and sex, as well as pooling all individuals together, making no assumption as to the number of populations present in the data set. The results suggest the presence of a genetically homogeneous unit off Northern Scotland, and a temporally stable pattern of isolation by distance determined predominantly by the divergence of the English Channel samples and, in 2003, by the Norwegian spring spawners. Our data suggest that the current view of North Sea herring as a unit-stock might be adequate, but confirm the considerable degree of demographic independence of the herring populations in the English Channel. Despite major recent population collapses, genetic data indicated no evidence of bottlenecks affecting the genetic diversity of extant North Sea herring populations. Finally, despite evidence of weak population structuring, we discuss the risks of underestimating population differentiation in marine fish of large population sizes, and with reference to herring population history and dynamics, we attempt to reconcile the existing theories on herring population structure.
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| 5. |
- André, Carl, 1958, et al.
(författare)
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Detecting population structure in a high gene-flow species, Atlantic herring (Clupea harengus) : direct, simultaneous evaluation of neutral vs putatively selected loci
- 2011
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 106:2, s. 270-280
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Tidskriftsartikel (refereegranskat)abstract
- In many marine fish species, genetic population structure is typically weak because populations are large, evolutionarily young and have a high potential for gene flow. We tested whether genetic markers influenced by natural selection are more efficient than the presumed neutral genetic markers to detect population structure in Atlantic herring (Clupea harengus), a migratory pelagic species with large effective population sizes. We compared the spatial and temporal patterns of divergence and statistical power of three traditional genetic marker types, microsatellites, allozymes and mitochondrial DNA, with one microsatellite locus, Cpa112, previously shown to be influenced by divergent selection associated with salinity, and one locus located in the major histocompatibility complex class IIA (MHC-IIA) gene, using the same individuals across analyses. Samples were collected in 2002 and 2003 at two locations in the North Sea, one location in the Skagerrak and one location in the low-saline Baltic Sea. Levels of divergence for putatively neutral markers were generally low, with the exception of single outlier locus/sample combinations; microsatellites were the most statistically powerful markers under neutral expectations. We found no evidence of selection acting on the MHC locus. Cpa112, however, was highly divergent in the Baltic samples. Simulations addressing the statistical power for detecting population divergence showed that when using Cpa112 alone, compared with using eight presumed neutral microsatellite loci, sample sizes could be reduced by up to a tenth while still retaining high statistical power. Our results show that the loci influenced by selection can serve as powerful markers for detecting population structure in high gene-flow marine fish species.
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| 7. |
- Polyak, Leonid, et al.
(författare)
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History of sea ice in the Arctic
- 2010
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 29:15-16, s. 1757-1778
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Tidskriftsartikel (refereegranskat)abstract
- Arctic sea-ice extent and volume are declining rapidly. Several studies project that the Arctic Ocean may become seasonally ice-free by the year 2040 or even earlier. Putting this into perspective requires information on the history of Arctic sea-ice conditions through the geologic past. This information can be provided by proxy records from the Arctic Ocean floor and from the surrounding coasts. Although existing records are far from complete, they indicate that sea ice became a feature of the Arctic by 47 Ma, following a pronounced decline in atmospheric pCO(2) after the Paleocene-Eocene Thermal Optimum, and consistently covered at least part of the Arctic Ocean for no less than the last 13-14 million years. Ice was apparently most widespread during the last 2-3 million years, in accordance with Earth's overall cooler climate. Nevertheless, episodes of considerably reduced sea ice or even seasonally ice-free conditions occurred during warmer periods linked to orbital variations. The last low-ice event related to orbital forcing (high insolation) was in the early Holocene, after which the northern high latitudes cooled overall, with some superimposed shorterterm (multidecadal to millennial-scale) and lower-magnitude variability. The current reduction in Arctic ice cover started in the late 19th century, consistent with the rapidly warming climate, and became very pronounced over the last three decades. This ice loss appears to be unmatched over at least the last few thousand years and unexplainable by any of the known natural variabilities.
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| 9. |
- Tarasov, P. E., et al.
(författare)
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A pollen-based biome reconstruction over the last 3.562 million years in the Far East Russian Arctic - new insights into climate-vegetation relationships at the regional scale
- 2013
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9332. ; 9:6, s. 2759-2775
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Tidskriftsartikel (refereegranskat)abstract
- The recent and fossil pollen data obtained under the frame of the multi-disciplinary international El'gygytgyn Drilling Project represent a unique archive, which allows the testing of a range of pollen-based reconstruction approaches and the deciphering of changes in the regional vegetation and climate. In the current study we provide details of the biome reconstruction method applied to the late Pliocene and Quaternary pollen records from Lake El'gygytgyn. All terrestrial pollen taxa identified in the spectra from Lake El'gygytgyn were assigned to major vegetation types (biomes), which today occur near the lake and in the broader region of eastern and northern Asia and, thus, could be potentially present in this region during the past. When applied to the pollen spectra from the middle Pleistocene to present, the method suggests (1) a predominance of tundra during the Holocene, (2) a short interval during the marine isotope stage (MIS) 5.5 interglacial distinguished by cold deciduous forest, and (3) long phases of taiga dominance during MIS 31 and, particularly, MIS 11.3. These two latter interglacials seem to be some of the longest and warmest intervals in the study region within the past million years. During the late Pliocene-early Pleistocene interval (i.e., similar to 3.562-2.200 Ma), there is good correspondence between the millennial-scale vegetation changes documented in the Lake El'gygytgyn record and the alternation of cold and warm marine isotope stages, which reflect changes in the global ice volume and sea level. The biome reconstruction demonstrates changes in the regional vegetation from generally warmer/wetter environments of the earlier (i. e., Pliocene) interval towards colder/drier environments of the Pleistocene. The reconstruction indicates that the taxon-rich cool mixed and cool conifer forest biomes are mostly characteristic of the time prior to MIS G16, whereas the tundra biome becomes a prominent feature starting from MIS G6. These results consistently indicate that the study region supported significant tree populations during most of the interval prior to similar to 2.730 Ma. The cold-and drought-tolerant steppe biome first appears in the reconstruction similar to 3.298 Ma during the tundra-dominated MIS M2, whereas the tundra biome initially occurs between similar to 3.379 and similar to 3.378 Ma within MIS MG4. Prior to similar to 2.800 Ma, several other cold stages during this generally warm Pliocene interval were characterized by the tundra biome.
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