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- Hagenblad, Jenny, et al.
(författare)
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Exploring the population genetics of genebank and historical landrace varierties
- 2012
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Ingår i: Genetic Resources and Crop Evolution. - : Springer. - 0925-9864 .- 1573-5109. ; 59:6, s. 1185-1199
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Tidskriftsartikel (refereegranskat)abstract
- Landrace accessions have long been recognized as an important source of genetic diversity for crop species, and landraces are stored in genebanks across the world as genetic resources for future crop development. Landraces are also an important part of the human cultural heritage and as such they have been used for genetic studies to make inferences about historical agriculture. However, surprisingly little is known about the within-accession diversity of landrace crops of different species. In order to evaluate the diversity of Swedish landraces we used microsatellite markers to genotype accessions of four species (barley, pea, oats and rye), both extant genebank material and 114-year-old seed samples of similar geographic origin and type. We found consistently high levels of within-population genetic diversity in the historical material, but varying and often lower diversity levels in the genebank accessions. We also make tentative conclusions about how representative the genebank material is to what was originally cultivated in its reported area of origin and suggest that the true identity of the genebank accessions is unclear and that historical seed collections should be a more appropriate material for the study of historical agriculture.
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| 2. |
- Nie, Xiang-Ping, et al.
(författare)
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Prey diversity and prey stomach contents affect astaxanthin levels in piscivorous fish
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Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590.
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Tidskriftsartikel (refereegranskat)abstract
- We analyzed astaxanthin concentrations and the composition of geometrical (E/Z) astaxanthin isomers in 631 tissue samples from the four chief fish species in the pelagic zone of the brackish Baltic Sea. Salmon and herring showed signs of astaxanthin deficiency, but cod and sprat did not. The isomers were distributed selectively in fish tissues, with highest proportions of all-E-astaxanthin in salmon gonads (71%) and lowest in herring gonads (19%). We discovered that the clupeids are no ideal prey for salmon and cod with respect to their high whole-body concentrations of astaxanthin Z-isomers, which have low bioavailability for salmon and cod. The salmon in the Baltic Sea is entirely dependent on herring and sprat for food intake while cod feeds on a more diverse diet, including crustaceans. This explains the normal low astaxanthin levels in the salmon in the Baltic Sea. Observed decreases in astaxanthin levels in the Baltic salmon during the last 50 years, which are related to a reproductional disturbance (M74 syndrome), can be explained by the here described poor quality of herring as astaxanthin source in combination with recorded changes in the feeding ecology of the Baltic salmon with less sprat and more herring in the diet today. Herring is inferior to sprat as astaxanthin source, especially in autumn when a salmon or cod obtains four times more bioavailable all-E-astaxanthin (by weight) from sprat than from herring. The Baltic herring is starving more than the sprat as a result of competition between the clupeids though fishing mortality and recruitment problems of the cod, their major predator during the last decades. Therefore, less crustacean astaxanthin (mainly all-E) is transferred directly to piscivorous fish from herring stomachs than from sprat stomachs.
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| 3. |
- Nie, Xiang-Ping, et al.
(författare)
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Why Baltic herring and sprat are weak conduits for astaxanthin from zooplankton to piscivorous fish
- 2011
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 56:3, s. 1155-1167
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Tidskriftsartikel (refereegranskat)abstract
- Atlantic salmon living in the brackish Baltic Sea have lower muscle pigmentation than populations elsewhere. The pigment in question is the antioxidant and vitamin A precursor astaxanthin, which is synthesized by crustaceans from algal carotenoids. Baltic salmon feed nearly exclusively on the clupeids sprat and herring. To evaluate astaxanthin availability to salmon we assessed astaxanthin levels and isomeric composition in their prey fish. We also analyzed astaxanthin dynamics in the dominant piscivorous fish in the Baltic Sea, the Atlantic cod. The geometrical E-(trans-) and Z-(cis-) isomers were distributed selectively in fish tissues, with highest E : Z ratios in salmon gonads (82 : 18) and lowest in herring gonads (24 : 76). Sprat and herring are not ideal prey with respect to their high whole-body concentrations of Z-isomers, which have low bioavailability for salmon and cod. These Z-isomers predominantly accumulate in the clupeid gonads. A crucial mechanism for the transport of astaxanthin from clupeids to piscivores is the direct transfer of crustacean astaxanthin (mainly all-E) from the clupeid stomachs. Low stomach astaxanthin content in clupeids decreases total astaxanthin transfer to higher trophic levels. In autumn, herring stomachs (including contents) had 12.5 times lower astaxanthin concentrations than sprat stomachs, and herring had 2.8 times less whole-body all-E-astaxanthin (by weight) than sprat. These results confirm recent reports of starvation in the Baltic herring, which may further decrease astaxanthin levels in the Baltic salmon. Cod did not have lower astaxanthin levels than their Atlantic counterpart, which may be attributed to their lower need for astaxanthin and higher food diversity.
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| 5. |
- Svensson, Filip, et al.
(författare)
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In situ warming strengthens trophic cascades in a coastal food web
- 2017
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 126:8, s. 1150-1161
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Tidskriftsartikel (refereegranskat)abstract
- Global warming may affect most organisms and their interactions. Theory and simple mesocosm experiments suggest that consumer top-down control over primary producer biomass should strengthen with warming, since consumer respiration increases faster with warming than plant photosynthesis. However, these predictions have so far not been tested on natural communities that have experienced warming over many generations. Natural systems display a higher diversity, heterogeneity and complexity than mesocosms, which could alter predicted effects of warming. Here we used an artificially heated part of the northern Baltic Sea (the Forsmark Biotest basin) to test how warming influences trophic interactions in a shallow coastal food web with four trophic levels: omnivorous fish, invertivorous fish, herbivorous invertebrates, and filamentous macroalgae. Monitoring of fish assemblages over six years showed that small invertivorous fish (gobiids, sticklebacks and minnows) were much less abundant in the heated basin than in unheated references areas. Stomach content analyses of the dominating omnivorous fish - Eurasian perch Perca fluviatilis - revealed a strikingly different diet within and outside the Biotest basin; gammarid crustaceans were the dominating prey at heated sites, whereas invertivorous fish (e.g. gobiids) dominated at unheated sites. A 45-day cage experiment showed that fish exclusion did not affect the biomass of algal herbivores (gastropods and gammarids), but reduced algal biomass in heated sites (but not unheated). This suggests that warming induced a trophic cascade from fish to algae, and that this effect was mediated by predator-induced changes in herbivore behavior, rather than number. Overall, our study suggests that warming has effectively compressed the food chain from four to three trophic levels (algae, gammarids and perch), which have benefitted the primary producers by reducing grazing pressure. Consequently, warming appears to have restructured this coastal food web through a combination of direct (physiological) and indirect (species interactions) effects.
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| 9. |
- Zie, Jenny, 1982-
(författare)
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Effects of warming on the green alga Cladophora glomerata : Ecological and genetic responses
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since the beginning of the 20th century, average global surface temperature has increased ~0.7 °C and the current scenarios predict that it will continue to rise additional 2-4 °C during the 21st century. Although many emphasise the need to better understand how warming affect ecosystems on both communities and species level, conclusive data is relatively scarce and our understanding of the effects of warming on community processes and species’ genetic and plastic responses to climate change is still in its infancy.This thesis aims at investigating the ecological and ecophysiological responses to warming of the vegetation in the littoral zone in the Baltic Sea and whether warming affects the genetic composition of the dominant algal species in this zone, the green alga Cladophora glomerata. Warming was studied by comparing properties of the vegetation and the genetic composition of C. glomerata grown in natural communities in unheated sites and heated sites with 3.4-10.3 °C higher water temperature. The studies in this thesis were performed in the Forsmark (60°24'N 18°09'E) and Oskarshamn (57°25'N 16°40'E) areas.The thesis shows that warming changed the community composition in Cladophora-belts, but not the species richness. It also shows that vegetation coverage and height increased with warming. The results also suggest that the vegetation at the heated sites was exposed to lower levels of oxidative stress. The results showed relatively high genetic diversity in the strictly asexual species C. glomerata, but that the genetic diversity decreases with warming. Further, all analyses showed differences between samples from heated and unheated sites and revealed specific patterns for samples from the heated sites. Additonally, C. glomerata at heated sites were more strongly affected by the effect of season than at the unheated sites. An analysis of the genotypic composition of C. glomerata from heated and unheated sites in the two different sub-basins of the Baltic Sea (Forsmark and Oskarshamn) revealed a congruent direction in selection to warming.In all, this new knowledge increases the understanding of how a habitat-forming filamentous alga in a coastal ecosystem may respond to current and future global warming.
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