| 61. |
- Aaltonen, Kristina, et al.
(författare)
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Nuclear and chloroplast microsatellites reveal extreme population differentiation and limited gene flow in the Aegean endemic Brassica cretica (Brassicaceae)
- 2007
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Ingår i: Molecular Ecology. - 0962-1083. ; 16:23, s. 4972-4983
-
Tidskriftsartikel (refereegranskat)abstract
- Nuclear and chloroplast microsatellite markers were used to study population structure and gene flow among seven Cretan populations of the Aegean endemic plant species Brassica cretica (Brassicaceae). Both nuclear and chloroplast markers revealed exceptionally high levels of population differentiation (overall FST = 0.628 and 1.000, respectively) and relatively little within-population diversity (overall HS = 0.211 and 0.000, respectively). Maximum-likelihood estimates of directional migration rates were low among all pairs of populations (average Nm = 0.286). There was no evidence that differences in flower colour between populations had any influence on historical levels of gene flow. In addition, a haplotype network showed that all five chloroplast haplotypes found in the sample were closely related. Together, these results suggest that current patterns of diversification in B. cretica are mainly a result of genetic drift during the last half million years. The main conclusions from the present study are consistent with the prevailing hypothesis that plant diversification in the Aegean region is driven by random rather than adaptive differentiation among isolated populations.
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| 62. |
- Aaltonen, Kristina, et al.
(författare)
-
The Evolution and Diversification of S-locus Haplotypes in the Brassicaceae Family.
- 2009
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Ingår i: Genetics. - : Oxford University Press (OUP). - 0016-6731 .- 1943-2631. ; 181:3, s. 977-984
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Tidskriftsartikel (refereegranskat)abstract
- Self-incompatibility (SI) in the Brassicaceae plant family is controlled by the SRK and SCR genes situated at the S locus. A large number of S haplotypes have been identified, mainly in cultivated species of the Brassica and Raphanus genera, but recently also in wild Arabidopsis species. Here, we used DNA sequences from the SRK and SCR genes of the wild Brassica species B. cretica, together with publicly available sequence data from other Brassicaceae species, to investigate the evolutionary relationships between S haplotypes in the Brassicaceae family. The results reveal that wild and cultivated Brassica species have similar levels of SRK diversity indicating that domestication has had but a minor effect on S-locus diversity in Brassica. Our results also show that a common set of S haplotypes were present in the ancestor of the Brassica and Arabidopsis genera, that only a small number of haplotypes survived in the Brassica lineage after its separation from Arabidopsis, and that diversification within the two Brassica dominance classes occurred after the split between the two lineages. We also find indications that recombination may have occurred between the kinase domain of SRK and the SCR gene in Brassica.
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| 63. |
- Aaltonen, Kristina, et al.
(författare)
-
Unequal segregation of SRK alleles at the S locus in Brassica cretica.
- 2008
-
Ingår i: Genetical Research. - 1469-5073. ; 90:3, s. 223-228
-
Tidskriftsartikel (refereegranskat)abstract
- In the Brassicaceae plant family, which includes the Arabidopsis and Brassica genera, self-incompatibility (SI) is controlled by genes at the S locus. Using experimental crosses, we studied the pattern of inheritance of S-locus alleles in the wild species Brassica cretica. Four full-sib families were established and unequal segregation of alleles at the SRK SI gene was found in one family. The segregation distortion acted in favour of a recessive (class II) allele and was best explained by some form of gametic-level selection. Our findings are discussed in the light of theoretical predictions of differential accumulation of deleterious mutations among S-locus alleles.
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| 64. |
- Aarestrup, K., et al.
(författare)
-
Survival and progression rates of anadromous brown trout kelts Salmo trutta during downstream migration in freshwater and at sea
- 2015
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 535, s. 185-195
-
Tidskriftsartikel (refereegranskat)abstract
- The marine migration of post-spawning anadromous fish remains poorly understood. The present study examined survival and progression rates of anadromous brown trout Salmo trutta L. after spawning (kelts) during downriver, fjord, and sea migration. Kelts (n = 49) were captured in the Danish River Gudenaa, tagged with acoustic transmitters and subsequently recorded by automatic receivers. Kelts spent on average 25 d moving down the 45 km river and through the brackish fjord. The fish entered the Kattegat Sea between 14 April and 30 May. Eighteen of the 49 kelts disappeared in the river and fjord during outward migration, likely due to mortality. Survival was not significantly related to gill Na+/K+-ATPase activity, suggesting that physiological adaptation to saltwater may be less critical for adults compared to juveniles (smolts). Of the 31 fish that entered the Kattegat Sea, 45% survived and returned to the fjord. The duration of the entire marine migration, from leaving to entering the river, was on average 163 d. The fish returned from the Kattegat Sea to the fjord between 22 July and 21 October. Upon return, the fish spent 1-90 d passing through Randers Fjord, with most individuals completing the reach within 4 d, suggesting that the kelts spent limited time foraging after returning to the fjord. The total survival during the entire marine migration, including the fjord, was a minimum of 29%. Our study provides data that are important for management of anadromous brown trout, and the high survival highlights that kelts may represent a valuable resource for both population reproduction and recreational fisheries.
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| 65. |
- Aarrestad, P. A., et al.
(författare)
-
Vegetation : Between Soils and Herbivores
- 2014
-
Ingår i: Elephants and Savanna Woodland Ecosystems. - Chichester, UK : Wiley-Blackwell. - 9781118858615 - 9780470671764 ; , s. 61-88
-
Bokkapitel (refereegranskat)abstract
- The vegetation of the study area in Chobe National Park is influenced by a range of factors, including inundation by the Chobe River, soil moisture and fertility, and the impacts of different-size grazers and browsers. This chapter focuses on how the structure and species composition of the present vegetation in northern Chobe National Park is related to recent herbivory by elephants, as agents shaping the vegetation, and by mesoherbivores acting as controllers or responders, along with abiotic controllers such as soil type and distance to the river. In the study, a two-way indicator species analysis classified the vegetation data into four more or less distinct plant community groups (i) Baikiaea plurijuga-Combretum apiculatum woodland, (ii) Combretum mossambicense-Friesodielsia obovata wooded shrubland, (iii) Capparis tomentosa-Flueggea virosa shrubland and (iv) Cynodon dactylon-Heliotropium ovalifolium floodplain, named after the TWINSPAN indicator or preferential species with high cover, and the relative amount of shrubs and trees.
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| 66. |
- Aas, O., et al.
(författare)
-
Salmonid stocking in five North Atlantic jurisdictions: Identifying drivers and barriers to policy change
- 2018
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Ingår i: Aquatic Conservation-Marine and Freshwater Ecosystems. - : Wiley. - 1052-7613. ; 28:6, s. 1451-1464
-
Tidskriftsartikel (refereegranskat)abstract
- New knowledge challenges long-established practices of fish stocking and transfer because of increasing scientific consensus that the release of cultivated fish can pose risks to biodiversity; however, stocking can also improve fisheries, creating difficult decision trade-offs regarding its use. Accordingly, controversy persists about fish stocking and transfer. No studies, however, have embraced a multinational perspective to understand the important governance dimensions of the success and failure of salmonid stocking and transfer policies. The present study has analysed the historical development and contemporary governance of the stocking and transfer of native and non-native salmonids of the genera Salmo, Salvelinus, and Oncorhynchus in five legislative units around the North Atlantic Ocean: the Atlantic Provinces of Canada, France, Germany, Norway, and Sweden. The study is based on the analyses of published and unpublished literature, and a survey of experts. Current salmonid stocking policies and practices varied significantly among jurisdictions; the degree of policy change varied, from radical and rapid changes de jure and de facto in Atlantic Canada and Norway to incremental mostly de jure changes in France and Germany. Rapid policy change in Atlantic Canada, Norway, and partly in Sweden can be explained by the socio-political importance of salmonid fisheries, stocking regulations based on policy objectives to conserve wild Atlantic salmon (Salmo salar), well-documented examples of the harmful consequences of transfers of non-native species, and well-developed vertical governance linkages. The policy changes resemble that of the 'punctuated equilibrium policy framework'. By contrast, France and Germany place less socio-political emphasis on salmonids, have stocking regulations less directed at wild salmonids, more local-level decision making, more species-rich fish communities, and little evidence of adverse ecological impacts of the transfer and stocking of salmonids. This has led to small, incremental changes in stocking policy de facto that are reflective of the 'advocacy coalition policy framework'.
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| 67. |
- Aastrup, Christian, et al.
(författare)
-
Size and immune function as predictors of predation risk in nestling and newly fledged jackdaws
- 2023
-
Ingår i: Animal Behaviour. - : Elsevier BV. - 0003-3472. ; 198, s. 73-84
-
Tidskriftsartikel (refereegranskat)abstract
- Prey choice by predators may be based on the potential prey's condition, for example resulting in substandard individuals running a higher risk of being predated. Over 5 years, we studied young jackdaws, Corvus monedula, to determine whether size and innate baseline immune function may predict predation risk by goshawks, Accipiter gentilis, during the nestling and early fledging phases. We measured body mass, wing length, tarsus length and four innate immune indices two to four times when nestlings were 12–29 days old. To determine which individuals had been predated during the nestling phase and shortly after fledging, we searched for metal rings of the jackdaws in the only goshawk territory close to the jackdaw colony. Nestling mortality before 12 days of age was entirely due to starvation, whereas between 12 days of age and fledging, mortality was mainly due to predation. Nestlings with smaller size (mass, wing, tarsus) and low lysis titre and haptoglobin concentrations were at a higher risk of being predated before fledging. Directly after fledging, individuals with short wings were preferentially predated, with no effects of body mass, tarsus length or any of the four immune indices measured at day 29 (i.e. shortly before fledging). That lower immune function and smaller size predict predation risk in nestlings may reflect that these individuals are of poor quality and/or lag behind in development. We hypothesize that hunger makes these nestlings sit closest to the entrance hole and hence become the first to be predated. For fledglings, our results suggest that poor flight ability makes individuals with short wings the easiest targets for avian predators.
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| 68. |
- Abadikhah, Marie, 1992, et al.
(författare)
-
Effect of anode material and dispersal limitation on the performance and biofilm community in microbial electrolysis cells
- 2023
-
Ingår i: Biofilm. - 2590-2075. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- In a microbial electrolysis cell (MEC), the oxidization of organic compounds is facilitated by an electrogenic biofilm on the anode surface. The biofilm community composition determines the function of the system. Both deterministic and stochastic factors affect the community, but the relative importance of different factors is poorly understood. Anode material is a deterministic factor as materials with different properties may select for different microorganisms. Ecological drift is a stochastic factor, which is amplified by dispersal limitation between communities. Here, we compared the effects of three anode materials (graphene, carbon cloth, and nickel) with the effect of dispersal limitation on the function and biofilm community assembly. Twelve MECs were operated for 56 days in four hydraulically connected loops and shotgun metagenomic sequencing was used to analyse the microbial community composition on the anode surfaces at the end of the experiment. The anode material was the most important factor affecting the performance of the MECs, explaining 54–80 % of the variance observed in peak current density, total electric charge generation, and start-up lag time, while dispersal limitation explained 10–16 % of the variance. Carbon cloth anodes had the highest current generation and shortest lag time. However, dispersal limitation was the most important factor affecting microbial community structure, explaining 61–98 % of the variance in community diversity, evenness, and the relative abundance of the most abundant taxa, while anode material explained 0–20 % of the variance. The biofilms contained nine Desulfobacterota metagenome-assembled genomes (MAGs), which made up 64–89 % of the communities and were likely responsible for electricity generation in the MECs. Different MAGs dominated in different MECs. Particularly two different genotypes related to Geobacter benzoatilyticus competed for dominance on the anodes and reached relative abundances up to 83 %. The winning genotype was the same in all MECs that were hydraulically connected irrespective of anode material used.
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| 69. |
- Abadikhah, Marie, 1992, et al.
(författare)
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Evidence of competition between electrogens shaping electroactive microbial communities in microbial electrolysis cells
- 2022
-
Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- In single-chamber microbial electrolysis cells (MECs), organic compounds are oxidized at the anode, liberating electrons that are used for hydrogen evolution at the cathode. Microbial communities on the anode and cathode surfaces and in the bulk liquid determine the function of the MEC. The communities are complex, and their assembly processes are poorly understood. We investigated MEC performance and community composition in nine MECs with a carbon cloth anode and a cathode of carbon nanoparticles, titanium, or stainless steel. Differences in lag time during the startup of replicate MECs suggested that the initial colonization by electrogenic bacteria was stochastic. A network analysis revealed negative correlations between different putatively electrogenic Deltaproteobacteria on the anode. Proximity to the conductive anode surface is important for electrogens, so the competition for space could explain the observed negative correlations. The cathode communities were dominated by hydrogen-utilizing taxa such as Methanobacterium and had a much lower proportion of negative correlations than the anodes. This could be explained by the diffusion of hydrogen throughout the cathode biofilms, reducing the need to compete for space.
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| 70. |
- Abadikhah, Marie, 1992
(författare)
-
Influence of electrode material and stochastic factors on the performance and microbial community assembly in microbial electrochemical systems
- 2022
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microbial electrolysis cells (MECs) are systems with microbial communities in the form of biofilms on electrode surfaces. The electrogenic bacteria in the anode biofilm act as catalysts for the oxidization of organic compounds, leading to release of electrons, generation of electrical current, and production of hydrogen and methane at the cathode. In addition to production of energy carriers, MECs can be used for other applications as well; for example, as biosensors to monitor biochemical oxygen demand or toxicity. The performance of MECs is determined by both deterministic and stochastic factors influencing the microbial communities on the electrode surfaces, most of which as still poorly understood. In this thesis, the effects of electrode materials on microbial community assembly and MEC performance was investigated. Two experiments were carried out. In the first, three cathode materials (carbon nanoparticles, titanium, and steel) were compared. In the second, three anode materials (carbon cloth, graphene, and nickel) were compared. The cathode materials had no significant effect on the performance of the MECs, as opposed to the anode materials where carbon cloth MECs had the highest current density and the shortest lag time during startup. The differences seen in lag time of replicate systems at the start of the experiment indicated a stochastic initial attachment of the electrogenic bacteria on the anode. Different microbial communities develop in the biofilms on the anodes and cathodes. Electrogens from the Desulfobacterota phylum dominated the anode, while various hydrogenotrophic methanogens, e.g., Methanobacterium, were found to dominate on the cathodes. Diversity and null model analysis of the electrode communities highlighted stochasticity and not electrode material as the important factor in the community assembly. Network analysis showed that the cathode communities had fewer negative interactions between taxa in comparison to the anode. Since hydrogen gas generated at the cathode surface can diffuse through the biofilm, all microorganisms on the cathode have access to the substrate, reducing the need for competition between species. In contrast, electrogens require a short distance to the anode to be able to use it as electron acceptor. Limited space on the anode and competition between electrogens shaped the anode communities and explain the higher number of negative interactions observed. Based on the findings in this thesis, it is suggested that stochastic factors have more influence than electrode material on the anode community even though there is a selective pressure for electrogenic bacteria.
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