| 1. |
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| 2. |
- Eriksson, Birgitta, et al.
(författare)
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TREFF-projektet
- 1986
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Rapport (refereegranskat)
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| 3. |
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| 4. |
- Eriksson, Torleif, 1955-
(författare)
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Migratory behaviour of Baltic salmon (Salmo salar L.) : adaptive significance of annual cycles
- 1988
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis evaluates the adaptive significance of annual cycles on the migratory behaviour of Baltic salmon (Salmo salar L.). The studies have included field experiments as well as laboratory studies gf maturity and migratory behaviour patterns of smolts and postsmolts mainly from the Angerman river population.Contrasting to the phenotypical elasticity in life-history traits, Baltic salmon was found to have a rather strict temporal organization of their annual behavioural patterns. Two year old smolted Baltic salmon showed drastic differences in migratory behaviour when compared in tanks containing either fresh or brackish water. Freshwater kept fish showed an annual cycle where downstream displacement in the upper water column was followed by a stationary behaviour, indicating a readaption to a freshwater life. Fish in brackish water behaved as a migratory fish throughout tne study. Baltic salmon also showed differences in maturation patterns in fresh and brackish water. Three summer old males detained in freshwater all matured sexually the following autumn. If transferred to sea and kept in net- pens a low proportion matured, mainly previously matured males. Furthermore there was a size- dependent relationship of sexual rematuration. Many small previously matured males did not migrate, similarly small previolusly matured males were unable to respond to shifts in the environment. With larger size the alternatives of sexual maturation and high growth rate wi more related to the environmental conditions the fish experienced.A hypothesis has been tested assuming that Baltic salmon migration is influenced by an annual time program. According to the hypothesis the migratory distance covered in the Baltic should be a result of a migratory activity sequence rather than a definite goal orientation. Fish detained before release generally showed a shorter distance between release point and area of recapture compared to fish released at normal time of smoltrun. The migratory distance appeared to be inversly related to the period of delay before release. A seasonal difference in migratory propensity was recorded.An instantaneous mortality curve for Baltic salmon during seaward migration and early sea-phase was estimated based on recapture data on sequentially related fish. The weekly mortality rate decreased from an initial mean of 271 during onset of migration, to 3.51 in mean during autumn. The high risk of mortality during the first part of migration indicated that strong selective forces act on a precise seasonal timing of migration.
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| 5. |
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| 6. |
- Amini, Hashem, et al.
(författare)
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Comparison of ultrasound and autopsy findings in pregnancies terminated due to fetal anomalies
- 2006
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Ingår i: Acta Obstetricia et Gynecologica Scandinavica. - : Wiley. - 0001-6349 .- 1600-0412. ; 85:10, s. 1208-1216
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Tidskriftsartikel (refereegranskat)abstract
- Objective. To compare antenatal diagnoses with autopsy findings in pregnancies terminated after ultrasound detection of fetal anomalies. A second aim was to study the quality of antenatal fetal diagnosis over time. Design. Retrospective, multicenter study over two consecutive six-year periods in Uppsala and Stockholm. Setting. Cases were identified through fetal autopsy reports. Subjects. Three hundred and twenty-eight fetuses from pregnancies terminated between 1992 and 2003 because of ultrasonographically diagnosed anomalies. Main outcome measures. The findings at the last ultrasound examination were compared with the autopsy reports. Results. In 299 cases (91.2%) ultrasound findings either exactly matched or were essentially similar to the autopsy findings. In 23 cases (7%) ultrasound findings were not confirmed at autopsy, but the postnatal findings were at least as severe as the antenatal ones. In six cases (1.8%) termination was performed for an anomaly which proved to be less severe than was predicted by ultrasound. The number of such cases was the same in both six-year periods, while the total number of cases increased from 113 in the first to 215 in the second period. Fetal examination provided further diagnostic information in 47% of the cases. In 10% a syndrome was disclosed. Conclusion. Termination of pregnancy was not always based on a correct antenatal diagnosis. All fetuses but one from terminated pregnancies had evident anomalies. In six cases (1.8%) the decision to terminate was based on suboptimal prognostic and diagnostic information. Fetal autopsy by an experienced perinatal pathologist is essential to provide a definitive diagnosis.
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| 7. |
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| 8. |
- Appel, Silke, et al.
(författare)
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Potential association of muscarinic receptor 3 gene variants with primary Sjogren's syndrome
- 2011
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Ingår i: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 70:7, s. 1327-1329
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Tidskriftsartikel (refereegranskat)abstract
- Background: Primary Sjögren's syndrome (pSS) is characterised by a chronic inflammation of exocrine glands. Salivary gland infiltrates, however, do not correlate well with disease symptoms, and a primary role for the salivary gland parenchyma in disease development has been suggested. Specifically, dysfunction of exocrine pathways involving the muscarinic receptor 3 (CHRM3) has been indicated. Objective: To investigate possible genetic divergence in the CHRM3 gene in patients with pSS. Methods: 530 patients with pSS and 532 controls from a combined Swedish and Norwegian cohort were genotyped for 84 single nucleotide polymorphisms (SNPs) distributed throughout CHRM3. Results: Genetic association was observed with five SNPs localised in intron 3 and 4 of CHRM3, the strongest being rs7548522 (minor allele frequency = 0.06, OR=1.93, 95% CI (1.24 to 3.01); p=0.0033). In addition, clinical parameters, including focus score, abnormal Schirmer's test and presence of autoantibodies, were associated with different SNPs in CHRM3. Conclusion: The study demonstrates a novel association of CHRM3 polymorphisms with pSS, suggesting a functional role for CHRM3 and the salivary gland parenchyma in the pathogenesis of pSS.
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| 9. |
- Arnell, Matilda, 1987-
(författare)
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Distribution patterns of fleshy-fruited woody plants at local and regional scales
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fleshy-fruited woody plants share a long history with humans, providing us with food and wood material. Because of this relation, we have actively moved some of these plants across landscapes and continents. In Sweden, these species are often found in open and semi-open habitats such as forest edges, their fruits are most often dispersed by birds and their flowers are, with some exceptions, pollinated by insects. In this thesis my overall aim was to map and analyse distribution patterns of fleshy-fruited woody plants in Sweden to expand our knowledge on the mechanisms governing their distributions. First, I mapped a population of the early flowering, fleshy-fruited shrub Daphne mezereum (common mezeron, tibast) and surveyed the reproduction and fruit removal of all individuals (chapter I). My main aim was to investigate to what extent reproduction and fruit removal was affected by local distribution patterns. Secondly, I mapped local distribution patterns of fleshy-fruited woody species and analysed spatial associations between life stages and species (chapter II). My main aim was to relate these spatial associations to predictions of how bird dispersal would shape the local distribution patterns and the hypothesis that birds create ‘wild orchards’. Thirdly, I digitized historical maps and surveyed fleshy-fruited woody species along transects across landscapes (chapter III). My aim was to examine the hypothesis that these species accumulate in open and semi open habitats created by human land use. Fourthly, I estimated range filling of woody plants in Sweden at a 1 km2 resolution (chapter IV). My aim was to compare these estimates among species with different dispersal systems to understand the effect of dispersal on the occupancy of woody species at regional scales.I found the distribution patterns of these species to be affected by past and present land use, supporting the hypothesis that these plants accumulate in open habitats. Occurrences of species in this guild in todays’ forest are positively related to past human land use (chapter III) and the density of D. mezereum increases with decreasing distances to forest edges (chapter I). This accumulation may in part be explained by the positive effect of forest edges on reproduction and fruit removal (chapter I). I further found local distribution patterns of this guild and the individual species to be aggregated (chapter I and II), and spatial associations between saplings and reproductive individuals to support the ‘orchard’ hypothesis (chapter II). The aggregated pattern of fruit-bearing individuals was positively related to fruit removal whereas aggregated flowering individuals was negatively related to fruit set (chapter I). On the regional scale, I found these species to occupy climatically suitable areas, or fill their potential ranges, to a less extent that wind dispersed trees and shrubs (chapter IV), which may indicate dispersal limitation.In conclusion, the behaviour of birds and humans have shaped, and still shape the current distribution of fleshy-fruited trees and shrubs in Sweden, resulting in accumulation in open habitats and locally aggregated distribution patterns. Changing land-use practices and potential mismatches between fruit maturation and bird dispersal with a changing climate may thus result in even lower chances of these species to fill their potential ranges, due to habitat losses and dispersal limitations at local and regional scales.
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| 10. |
- Arnell, Matilda, et al.
(författare)
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Does historical land use affect the regional distribution of fleshy-fruited woody plants?
- 2019
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 14:12
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Tidskriftsartikel (refereegranskat)abstract
- Species richness and composition of current vegetation may reflect historical land use. We develop and examine the hypothesis that regional distribution and richness of fleshy-fruited woody plants, a group sharing life-form and dispersal system, reflect historical land use in open or semi-open habitats. Historical land use was based on maps from around the year 1900 for two regions in Sweden, and field data was gathered from surveys made in these regions. Species richness was positively related to historical land use indicated as open habitat in 1900. In one of the regions, five out of nine examined species were positively related to historical land use (with historical effect R-2 ranging between 0.03 and 0.22). In the other region, we found a weaker positive relationship with historical land use in two out of nine examined species (R-2 0.01 and 0.02). We conclude that current occurrence and richness of fleshy-fruited woody species is partly a legacy of historical land use, and that regions may vary in this respect. Based on a comparison between the two regions examined here, we discuss some potential causes behind this variation.
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| 11. |
- Arnell, Matilda, et al.
(författare)
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Landscape-scale range filling and dispersal limitation of woody plants
- 2022
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 49:11, s. 2028-2036
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Tidskriftsartikel (refereegranskat)abstract
- Aim: The extent to which species fill their predicted current ranges and the underlying process of dispersal limitation have implications for species' abilities to track climate change. Range filling is intimately related to spatial scale, yet range filling estimates at high resolutions are largely lacking. In this study, we aim to estimate range filling and dispersal limitation at a high resolution for woody plants with different dispersal systems and habitat affinities.Location: Sweden.Taxon: All genera of woody plants (trees and shrubs).Methods: We estimated landscape-scale range filling for 64 species. Two main dispersal systems, vertebrate dispersal and abiotic dispersal, occurred among these species. Range filling was estimated as the realized range divided by the potential range, that is, the occupied proportion of a species' modelled range, at a 1 km2 resolution. We estimated potential ranges using species distribution models and realized ranges from presence records. To increase the likelihood that absences represented true absences the estimations were restricted to areas with high sampling effort. We tested the effects of dispersal system on range filling, controlling for species' habitat affinities.Results: Vertebrate-dispersed woody species had significantly lower landscape-scale range filling than species with abiotic dispersal. Range filling was also linked to habitat affinity. Species associated with intermediate levels of light and moisture had the highest range filling estimates.Main conclusions: Landscape-scale range filling of woody species is linked to their dispersal traits. When controlling for habitat affinity, our result suggests that dispersal limitation partly explains the lower occupancy in suitable habitat found for vertebrate-dispersed plants. Given that vertebrate-dispersed species fail to reach suitable habitats at this scale, they are less likely to track changes in climate than woody plants with abiotic dispersal.
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| 12. |
- Arnell, Matilda, et al.
(författare)
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Local distribution patterns of fleshy-fruited woody plants - testing the orchard hypothesis
- 2021
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 44:3, s. 481-492
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Tidskriftsartikel (refereegranskat)abstract
- Plant distribution patterns are influenced by many different factors. We examined mechanisms behind local distribution patterns of boreo-nemoral fleshy-fruited woody plants with seed dispersal mainly mediated by birds. It has been suggested that guilds of these plants develop 'orchards', i.e. locally aggregated occurrences composed of several species. We analysed spatially explicit occurrence data of different life stages of a local guild of fleshy-fruited woody plants in south-eastern Sweden, and conducted a seedling recruitment experiment for a subset of ten species. Spatial point pattern analyses showed that the guild of fleshy-fruited species was aggregated at small (< 10 m) spatial scales. Saplings were more common under canopies of heterospecific reproductive individuals than expected by chance. These results show that the local guild of fleshy-fruited species is distributed as orchards, i.e. clusters consisting of individuals of different species and life stages. We found no evidence of negative distance dependence between saplings and reproductive conspecific individuals. Results from the recruitment experiment suggest that recruitment is seed limited and generally low among the studied species. At the site-scale (circular areas with 50 m radius), there was no difference in seedling recruitment between sites with and without reproductive conspecific individuals for most species included in the recruitment experiment. This further suggests that the aggregated patterns found are not simply a result of spatial concordance in suitable habitats across life stages. Instead, we suggest that the sheer number of seeds from species in the guild deposited under the crowns of fruit bearing individuals is the main mechanism behind the build-up of orchards. Although further studies are needed to fully disentangle the processes underlying the observed patterns of local diversity, we argue that describing patterns and contrasting them to the predictions of ecologically relevant hypotheses is a useful first step.
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| 13. |
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| 14. |
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| 15. |
- Arnell, Matilda, 1987-, et al.
(författare)
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Reproductive success, fruit removal and local distribution patterns in the early-flowering shrub Daphne mezereum
- 2023
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Ingår i: Nordic Journal of Botany. - 0107-055X .- 1756-1051. ; :10
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Tidskriftsartikel (refereegranskat)abstract
- In insect-pollinated, bird-dispersed plants, both investment in reproduction and reproductive success involve interactions between plants and their pollinators and dispersers. The outcome of these plant–animal interactions may be affected by the number of flowers and fruits, as well as by the plants' local environment and by spatial associations among plants. In this study we mapped the spatial distribution of individuals in a population of the early flowering, fleshy-fruited shrub Daphne mezereum, in a forest in boreo-nemoral Sweden. For all mapped individuals we collected data on numbers of flowers and fruits and fruit removal, for three consecutive years. We analysed spatial associations among individuals, and the effects on reproductive performance and fruit removal of plant height, numbers of flowers and fruits, distance to forest edge, and neighbouring flower and fruit density. Our results show that the density of D. mezereum increases with increasing proximity to forest edge. The number of flowers produced, as well as fruit set and fruit removal, show the same positive relationship with increasing proximity to forest edges. We further show that individuals are aggregated up to distances of about 10 m. The flower production of neighbouring conspecific individuals within 10 m is negatively related to fruit set whereas the fruit production of neighbours is positively related to fruit removal. Our main conclusion is that the spatial distribution of D. mezereum affects reproductive success and fruit removal, which in turn has the potential to feed back to the spatial distribution pattern. Combining studies of reproduction with spatial analyses is important to advance our understanding of the dynamics of plant populations.
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| 16. |
- Axin, Mikael, 1984-, et al.
(författare)
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Dynamic Analysis of Single Pump, Flow Controlled Mobile Systems
- 2011
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Ingår i: The Twelfth Scandinavian International Conference on Fluid Power, SICFP'11. - 9789521525193 ; , s. 223-238
-
Konferensbidrag (refereegranskat)abstract
- Interest has increased in flow controlled systems in the field of mobile fluid power. The capital distinction between traditional load-sensing (LS) systems and flow controlled systems is that the pump is controlled based on the operator’s total flow demand rather than maintaining a certain pressure margin over the maximum load pressure. One of the main advantages of flow controlled systems is the absence of the feedback of the highest load pressure to the pump controller. In this paper, a dynamic analysis is performed where flow controlled and LS systems are compared. It is shown how instability can occur in LS systems due to the pump controller and proven that no such instability properties are present in flow controlled systems. A drawback with one type of flow controlled system is that the highest load dynamically will disturb the lighter loads. This paper shows a novel way to optimize the damping in such systems by controlling the opening position of the directional valve independently of the flow. The mentioned disturbance between the highest load to the others can thereby be reduced.
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| 17. |
- Axin, Mikael, 1984-, et al.
(författare)
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Energy Efficient Load Adapting System Without Load Sensing : Design and Evaluation
- 2009
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Konferensbidrag (refereegranskat)abstract
- In load sensing systems, the pump pressure is controlled in a closed loop control mode. In this paper, a system solution where the displacement of the pump is controlled directly from the operator's demand is studied. Both the stability and the response is thereby improved. It also implies a better energy efficiency since the pump pressure will be adapted according to the point of operation with no additional pressure margin needed. In some mobile applications, pressure compensation is required to avoid load interference. When using common pre compensators in a displacement controlled system, the pump and the valve will both control the flow. A better solution would be to control the flow by the pump and utilize the valve as a flow divider. This can be achieved by using flow sharing compensators. It also allows further energy savings since the maximum restriction area of the main spool at one of the loads can be utilized independent of the flow delivered by the pump. This paper addresses the problem with using common pre compensators in displacement controlled systems and analyses and compares both a traditional load sensing system and an open controlled pump solution with flow sharing compensators. Measurements on a wheel loader application equipped with the system presented in this paper shows a decreased energy consumption of 14 % for the working hydraulics compared to a load sensing system during a short loading cycle, provided that the pump is not saturated.
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| 18. |
- Bachmann, Jörg Alexander, 1989-
(författare)
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Evolutionary consequences of dominance at the Brassicaceae self-incompatibility locus
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Self-incompatibility (SI) is a genetic mechanism that allows plants to enforce outcrossing by rejecting self-pollen and pollen from close relatives. In the Brassicaceae, SI is sporophytic and controlled by the self-incompatibility locus (S-locus). The S-locus harbors two tightly linked genes SRK and SCR, which encode the female and male SI specificity determinants, respectively. S-locus heterozygotes often only express the S-specificity of the more dominant allele, and at the pollen level such dominance relationships are mediated by small RNAs (sRNAs). The S-locus is thus an example of a locus under strong balancing selection, where dominance modifiers have evolved.In this thesis, I investigate the consequences of S-locus dominance for plant mating system evolution and allopolyploid speciation. I further investigate evolutionary conservation and sequence-level effects of dominance relationships among S-alleles. For this purpose, I used the crucifer genus Capsella as a model system.First, I demonstrated that targeted long-read sequencing results in structurally accurate assemblies of full-length S-haplotype sequences, and that indel errors in such assemblies can be corrected using short reads. Second, I investigated the genetic basis of loss of SI, the first step in the evolution of self-fertilisation, in the self-compatible (SC) Capsella orientalis. I found that loss of SI was dominant and mapped to the S-locus, where C. orientalis harbored a fixed coding frameshift deletion in SCR that is likely to lead to loss of male specificity. I further identified a sRNA-based dominance modifier that is associated with dominant suppression of recessive SCR alleles. Taken together, these results suggest that loss of SI in C. orientalis involved a dominant S-haplotype, suggesting that dominant haplotypes may be favored under conditions that select for loss of SI. Third, I show that a dominant S-haplotype may also have contributed to the shift to SC in the widespread allotetraploid Capsella bursa-pastoris. Fourth, I showed that dominance relationships at the S-locus are largely conserved between the SI outcrossing species C. grandiflora and Arabidopsis halleri which diverged ~8 Mya. I also found that dominant S-haplotypes accumulate more transposable elements than recessive S-haplotypes, in line with expected sequence-level consequences of S-locus dominance. In sum, this thesis provides new insights into the broad conservation of dominance hierarchies at the Brassicaceae S-locus, and the role of dominant S-alleles in allopolyploid speciation and plant mating system shifts.
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| 19. |
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| 20. |
- Beijer, Elisabeth, et al.
(författare)
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Utvärderingsverkstäder i välfärdsverksamheter : studier av verkstädernas kvalitet och nytta
- 2011
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Med inspiration från aktionsforskningen har olika former av förändringsinriktad och deltagarbaserad forskning och utvecklingsarbete utvecklats, under beteckningar som forsknings- eller FoU-cirklar (Socialstyrelsen, 2002), participatorisk aktionsforskning (Participatory Action Research, PAR) (Holmer & Starrin, 1993), handlingsorienterat forskningssamarbete (Co-operative Inquiry) (Reason & Heron, 1986; Hummelvoll, 2006). Dessa olika arbetssätt förenas i en gemensam syn på hur kunskap kan utvecklas, spridas och användas: gemensamt och i samarbete, och inte utifrån ett ’top-down-perspektiv’. Utvärderingsverkstäder (i fortsättningen förkortat UV), som utgår från denna tradition, arrangeras av FoU-enheter inom välfärdsområdet, och/eller av högskola/universitet. I dessa verkstäder träffas en grupp deltagare tillsammans med utvärderingskunniga ledare från FoU-enheten/högskolan. Deltagarna genomför med stöd från ledarna och de övriga deltagarna utvärderingar, eller utvecklar system för utvärdering, på uppdrag av sina respektive organisationer.Syftet med detta paper är att redovisa och diskutera tio års erfarenheter från UV vid fyra FoU-enheter och en högskola i Mellansverige, ur deltagarnas och deras organisationers, samt ledarnas och de ansvariga enheternas/högskolans perspektiv.
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| 21. |
- Beijer, Elisabeth, et al.
(författare)
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Verkstäder för utvärdering i välfärdsverksamheter : erfarenheter från några svenska FoU-enheter och högskolor
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I denna rapport beskrivs och värderas erfarenheter från utvärderingsverkstäder, som är en pedagogisk form för att simultant lära om utvärdering och att genomföra utvärderingar inom välfärdsområdet. Rapporten bygger på studier av utvärderingsverkstäder liksom på författarnas egna erfarenheter från att bedriva verkstäder. Studien har genomförts inom ramen för Nätverket för utvärderingsverkstäder (Nuv). Initiativet till Nuv togs 2008 från Mälardalens Högskola och dess utvärderingsakademi. Nätverket etablerades mellan de enheter vars medarbetare medverkar i denna rapport; FoU Välfärd Värmland (Bengt G Eriksson), FoU i Väst/GR (Elisabeth Beijer), Mälardalens Högskola och FoU i Sörmland (Kari Jess, Laila Niklasson, Ove Karlsson Vestman) och FoU Sjuhärad Välfärd (Per-Åke Karlsson). Jennifer C Greene, gästprofessor vid Mälardalens högskola, medverkade under en tid i nätverket och bidrar även i denna antologi. Tanken med Nuv är att samla och sprida erfarenheter från redan genomförda verkstäder, för att på så sätt bidra till en utveckling där flera utvärderingsverkstäder kommer till stånd och till att förbättra arbetsmodellen på basis av gjorda erfarenheter. Denna antologi är ett led i detta. Rapporten har antologins form där varje författare svarar för innehållet i respektive kapitel. Grundmaterialet för kapitlen utgörs av de studier vi genomfört gemensamt samt erfarenheter från att leda utvärderingsverkstäder. Våren 2009 genomförde vi tillsammans en enkätundersökning riktad till deltagare i utvärderingsverkstäderna. Vi vill passa på att tacka deltagarna som tog sig tid att besvara enkäten. Dessutom genomfördes något senare ett antal intervjuer med några deltagare i utvärderingsverkstäderna liksom med några av deras chefer (tillika uppdragsgivare för utvärderingsuppdragen). Även dessa vill vi tacka för att de välvilligt låtit sig intervjuas om sina erfarenheter från verkstäderna. Vår förhoppning är att antologin ska bidra till att sprida kunskap om utvärderingsverkstäder, bidra till utveckling av metodiken samt inspirera till ytterligare verkstäder.
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| 22. |
- Björn, Eriksson, 1981-, et al.
(författare)
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Energy saving system utilizing LQ-technique design
- 2009
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Ingår i: Proceedings of the Seventh International Conference on Fluid Power Transmission and Control. - Beijing : Beijing World Publishing Corporation. ; , s. 224-229
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the control of individual metering systems. This paper deals with the control of an individual metering system that could be used for reducing metering losses by enabling recuperation and regeneration operation. A system that utilizes individual metering is more flexible than a conventional system since there are more control signals and thereby more outputs to control. Energy saving aspects is among the main reasons for the research on this kind of system, but there is also an opportunity of improvements of the dynamics compared to a conventional system. In this paper an approach with LQtechnique are presented for improvements of system dynamics. Since all states in the system can not be measured a state observer is also considered in the control design. These work present simulations, implementations in a real world forwarder application and results from verifying experiments.
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| 23. |
- Bolmgren, Kjell, 1966-
(författare)
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Adaptation and Constraint in the Plant Reproductive Phase
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Conservatism is a central theme of organismic evolution. Related species share characteristics due to their common ancestry. Some concern have been raised among evolutionary biologists, whether such conservatism is an expression of natural selection or of a constrained ability to adapt.This thesis explores adaptations and constraints within the plant reproductive phase, particularly in relation to the evolution of fleshy fruit types (berries, drupes, etc.) and the seasonal timing of flowering and fruiting. The different studies were arranged along a hierarchy of scale, with general data sets sampled among seed plants at the global scale, through more specific analyses of character evolution within the genus Rhamnus s.l. L. (Rhamnaceae), to descriptive and experimental field studies in a local population of Frangula alnus (Rhamnaceae). Apart from the field study, this thesis is mainly based on comparative methods explicitly incorporating phylogenetic relationships. The comparative study of Rhamnus s.l. species included the reconstruction of phylogenetic hypotheses based on DNA sequences.Among geographically overlapping sister clades, biotic pollination was not correlated with higher species richness when compared to wind pollinated plants. Among woody plants, clades characterized by fleshy fruit types were more species rich than their dry-fruited sister clades, suggesting that the fleshy fruit is a key innovation in woody habitats. Moreover, evolution of fleshy fruits was correlated with a change to more closed (darker) habitats.An independent contrast study within Rhamnus s.l. documented allometric relations between plant and fruit size. As a phylogenetic constraint, allometric effects must be considered weak or non-existent, though, as they did not prevail among different subclades within Rhamnus s.l. Fruit size was correlated with seed size and seed number in F. alnus. This thesis suggests that frugivore selection on fleshy fruit may be important by constraining the upper limits of fruit size, when a plant lineage is colonizing (darker) habitats where larger seed size is adaptive.Phenological correlations with fruit set, dispersal, and seed size in F. alnus, suggested that the evolution of reproductive phenology is constrained by trade-offs and partial interdependences between flowering, fruiting, dispersal, and recruitment phases. Phylogenetic constraints on the evolution of phenology were indicated by a lack of correlation between flowering time and seasonal length within Rhamnus cathartica and F. alnus, respectively. On the other hand, flowering time was correlated with seasonal length among Rhamnus s.l. species. Phenological differences between biotically and wind pollinated angiosperms also suggested adaptive change in reproductive phenology.
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| 24. |
- Bolmgren, Kjell, et al.
(författare)
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Are mismatches the norm? Timing of flowering, fruiting, dispersal and germination and their fitness effects in Frangula alnus (Rhamnaceae)
- 2015
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 124, s. 639-648
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Tidskriftsartikel (refereegranskat)abstract
- The close morphological and temporal links between phases of plant growth and reproduction call for integrated studies incorporating several reproductive phases from flowering to recruitment, and associated plant-animal interactions. Phenological strategies, as well as plastic phenological response to climate change, incorporate complex interactions between developmental constraints, pollination and seed dispersal. Relationships between reproductive phenology and components of fitness were studied for two years in the north-temperate, self-incompatible, insect-pollinated, and bird-dispersed shrub Frangula alnus (Rhamnaceae). Fruit set, dispersal, germination and juvenile survival, as well as seed mass and juvenile size were measured in relation to flowering, fruiting and germination time. The results suggest that effects of flowering and fruiting time prevailed in subsequent phases, to some extent as far as to the juvenile phase, but effects of timing were complex and had partly opposing effects on different fitness components. Early flowers had higher fruit-set and experiments indicated that synchronous peak flowering increased fruit-set, but later flowers had higher seed mass. Peak fruiting was not associated with peak dispersal. Late fruits derived from late flowers promoted dispersal. Juvenile recruitment was enhanced by increasing seed size. We conclude that the phenology of flowering and fruiting in F. alnus comprises several features, each with different and sometimes counteracting effects on fitness components. From a general perspective, this result implies that we should not expect to find finely tuned matches in timing specifically between flowering and pollinators, and fruiting and seed dispersing birds.
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| 25. |
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| 26. |
- Bolmgren, Kjell, et al.
(författare)
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Fleshy fruits – origins, niche shifts, and diversification.
- 2005
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 109:2, s. 255-272
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Tidskriftsartikel (refereegranskat)abstract
- We examined shifts in fruit type, fleshy vs non-fleshy, in relation to habitat-related niche shifts, species richness, and historical distribution, in 50 phylogenetically independent plant lineages. Each lineage consisted of a sister-group pair of fleshy vs non-fleshy taxa and their outgroup. Niche shifts were assessed based on plant community characteristics. Two niche dimensions assumed to reflect community dynamics were derived: spatial predictability of disturbances and canopy closure. Phylogenetically independent origins of fleshy fruit types (1) were correlated with changes to habitats characterized by more shaded and spatially more unpredictable disturbances, (2) had an opposite effect on species richness in woody and herbaceous clades, enhancing species richness in woody clades, and (3) were continuously distributed over a period covering the last 70 million years. These results support the hypothesis that fleshy fruit evolution is driven by vegetation dynamics, and suggest that the strength of frugivore mediated selection on fleshy fruits increases when recruitment sites are spatially unpredictable and/or characterized by low light conditions.
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| 27. |
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| 28. |
- Bolmgren, Kjell, et al.
(författare)
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Seed mass and the evolution of fleshy fruits in angiosperms
- 2010
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 119:4, s. 707-718
-
Forskningsöversikt (refereegranskat)abstract
- Fleshy fruits, like drupes and berries, have evolved many times through angiosperm history. Two hypotheses suggest that fleshy fruit evolution is related to changes in the seed mass fitness landscape. The reduced dispersal capability following from an increase in seed mass may be counterbalanced by evolution of traits mediating seed dispersal by animals, such as fleshy fruits. Alternatively, increasing availability and capabilities of frugivores promote evolution of fleshy fruits and allow an increase in seed size. Both these hypotheses predict an association between evolution of fleshy fruits and increasing seed size. We investigated patterns of fruit and seed evolution by contrasting seed mass between fleshy and non-fleshy fruited sister clades. We found a consistent association between possession of fleshy fruits and heavier seeds. The direction of fruit type change did not alter this pattern; seed mass was higher in clades where fleshy fruits evolved and lower in clades where non-fleshy fruits evolved, as compared to their sister clades. These patterns are congruent with the predictions from the two hypotheses, but other evidence is needed to distinguish between them. We emphasize the need to integrate studies of seed disperser effectiveness, seed morphology, and plant recruitment success to better understand the frugivores' role in fleshy fruit evolution.
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| 29. |
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| 30. |
- Callebaut, Gilles, et al.
(författare)
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6G Radio Testbeds: Requirements, Trends, and Approaches
- 2024
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Ingår i: IEEE Microwave Magazine. - 1527-3342 .- 1557-9581. ; 25:4, s. 14-31
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Tidskriftsartikel (refereegranskat)abstract
- The proof of the pudding lies in eating, and that is why 6G testbeds are essential in the progress toward the next generation of wireless networks. Theoretical research toward 6G wireless networks proposes advanced technologies to serve new applications and drastically improve energy performance. Testbeds are indispensable to validate these new technologies under more realistic conditions. This article clarifies the requirements for 6G radio testbeds, reveals trends, and introduces approaches toward their development.
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| 31. |
- Chiotis, Konstantinos, et al.
(författare)
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Imaging in-vivo tau pathology in Alzheimer's disease with THK5317 PET in a multimodal paradigm
- 2016
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Ingår i: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer Science and Business Media LLC. - 1619-7070 .- 1619-7089. ; 43:9, s. 1686-1699
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Tidskriftsartikel (refereegranskat)abstract
- Purpose The aim of this study was to explore the cerebral distribution of the tau-specific PET tracer [F-18]THK5317 (also known as (S)-[F-18]THK5117) retention in different stages of Alzheimer's disease; and study any associations with markers of hypometabolism and amyloid-beta deposition. Methods Thirty-three individuals were enrolled, including nine patients with Alzheimer's disease dementia, thirteen with mild cognitive impairment (MCI), two with non-Alzheimer's disease dementia, and nine healthy controls (five young and four elderly). In a multi-tracer PET design [F-18]THK5317, [C-11] Pittsburgh compound B ([C-11]PIB), and [F-18]FDG were used to assess tau pathology, amyloid-beta deposition and cerebral glucose metabolism, respectively. The MCI patients were further divided into MCI [C-11]PIB-positive (n=11) and MCI [C-11]PIB-negative (n=2) groups. Results Test-retest variability for [F-18]THK5317-PET was very low (1.17-3.81 %), as shown by retesting five patients. The patients with prodromal (MCI [C-11]PIB-positive) and dementia-stage Alzheimer's disease had significantly higher [F-18]THK5317 retention than healthy controls (p=0.002 and p=0.001, respectively) in areas exceeding limbic regions, and their discrimination from this control group (using the area under the curve) was >98 %. Focal negative correlations between [F-18]THK5317 retention and [F-18]FDG uptake were observed mainly in the frontal cortex, and focal positive correlations were found between [F-18]THK5317 and [C-11] PIB retentions isocortically. One patient with corticobasal degeneration syndrome and one with progressive supranuclear palsy showed no [C-11]PIB but high [F-18]THK5317 retentions with a different regional distribution from that in Alzheimer's disease patients. Conclusions The tau-specific PET tracer [F-18]THK5317 images in vivo the expected regional distribution of tau pathology. This distribution contrasts with the different patterns of hypometabolism and amyloid-beta deposition.
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| 32. |
- Cortés-González, Jeff R, et al.
(författare)
-
Early salvage radiation therapy combined with short-term hormonal therapy in recurrent prostate cancer after radical prostatectomy: Single-institution 4-year data on outcome, toxicity, health-related quality of life and co-morbidities from 184 consecutive patients treated with 70 Gy.
- 2013
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Ingår i: International journal of oncology. - : Spandidos Publications. - 1791-2423 .- 1019-6439. ; 42:1, s. 109-17
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the role of 70Gy salvage radiotherapy (SRT) combined with short-term neoadjuvant hormonal therapy (NHT) in the treatment of recurrent disease after radical prostatectomy (RP), and to consider quality of life (QoL), survival outcomes and impact of co-morbidities on treatment-related rectal-genitourinary toxicity. Electronic records of 184 SRT patients treated consecutively between October 2001 and February 2007 were analyzed. Median age was 64 years (median follow-up 48months). NHT was given to 165 patients (median 3 months). Pre-RP and pre-SRT PSA, PSA doubling time, Gleason score (GS), seminal vesicle invasion (SVI) and detectable post-SRT PSA were recorded. Any detectable PSA or PSA >0.1 ng/ml + nadir was considered biochemical failure (BcF). The Charlson co-morbidity index was used to correlate co-morbidities and rectal-genitourinary toxicity. Scores from the health-related QoL EORTC QLQ-C30 and PR-25 questionnaires were also evaluated. In 116 (63%) patients, a long-lasting curative effect was indicated by undetectable PSA levels. In univariate analysis, using BcF as an outcome variable, p<0.001 was found for GS, pre-SRT PSA, SVI and detectable post-SRT PSA. Multivariate analysis showed p=0.01 for SVI, p=0.09 for GS, and detectable post-SRT PSA (p=0.01); with metastases as an outcome variable, only SVI was significant (p=0.007). Cancer-specific and overall survival were 99 and 95%, respectively. Although microscopy showed SVI or GS 8-10 in the prostatectomy specimens 17/40(43%) and 13/29 (45%), respectively, of patients still showed undetectable PSA at long-term follow-up (median 55 months) after SRT. Likewise, 11/31 (36%) patients with pre-SRT PSA >1.0 ng/ml and 80/134 (60%) patients with PSA doubling time (PSADT) <10 still showed undetectable PSA after 50 months. Slightly elevated acute and late rectal-genitourinary grade 3-4 toxicity was observed. No association with co-morbidity/toxicity was found. EORTC QLQ-C30 scores were similar to or slightly better than reference values. SRT with 70 Gy combined with 3-month NHT results in long-term undetectable PSA in >50% of patients with recurrence after RP with acceptable rectal-genitourinary toxicity and without negatively affecting long-term QoL. Non-metastatic patients should not be disqualified from receiving SRT although presenting with poor prognostic factors at surgery.
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| 33. |
- Cousins, Sara A. O., et al.
(författare)
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After the hotspots are gone: land use history and grassland plant species diversity in a strongly transformed agricultural landscape
- 2008
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Ingår i: Applied Vegetation Science. - : Wiley. - 1402-2001 .- 1654-109X. ; 11:3, s. 365-374
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Tidskriftsartikel (refereegranskat)abstract
- Question: We asked how landscape configuration and present management influence plant species richness and abundance of habitat specialists in grasslands in a ‘modern’ (much exploited and transformed) agricultural Swedish landscape.Location: Selaön, south-eastern Sweden (59°24' N, 17°10' E).Methods: Present and past (150 and 50 years ago) landscape pattern was analysed in a 25 km2 area. Species richness was investigated in 63 different grassland patches; grazed and abandoned semi-natural grasslands, and grazed ex-arable fields. Influence of landscape variables; area, past and present grassland connectivity, present management on total species richness, density and abundance of 25 grassland specialists was analysed.Results: Semi-natural grasslands (permanent unfertilised pastures or meadows formed by traditional agricultural methods) had declined from 60% 150 years ago to 5% today. There was a significant decline in species richness and density in abandoned semi-natural grasslands. Total species richness was influenced by present management, size and connectivity to present and past grassland pattern. Landscape variables did not influence species density in grazed semi-natural grassland suggesting that maintained grazing management makes grassland patches independent of landscape context. The abundance of 16 grassland specialists was mainly influenced by management and to some extent also by landscape variables.Conclusion: Although species richness pattern reflect management and to some extent landscape variables, the response of individual species may be idiosyncratic. The historical signal from past landscapes is weak on present-day species richness in highly transformed, agricultural landscapes. Generalizations of historical legacies on species diversity in grasslands should consider also highly transformed landscapes and not only landscapes with a high amount of diversity hotspots left.
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| 34. |
- Cousins, Sara A. O., et al.
(författare)
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Effects of historical and present fragmentation on plant species diversity in semi-natural grasslands in Swedish rural landscapes.
- 2007
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Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 22:5, s. 723-730
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Tidskriftsartikel (refereegranskat)abstract
- Habitat loss and fragmentation of natural and semi-natural habitats are considered as major threats to plant species richness. Recently several studies have pinpointed the need to analyse past landscape patterns to understand effects of fragmentation, as the response to landscape change may be slow in many organisms, plants in particular. We compared species richness in continuously grazed and abandoned grasslands in different commonplace rural landscapes in Sweden, and analysed effects of isolation and area in three time-steps (100 and 50 years ago and today). Old cadastral maps and aerial photographs were used to analyse past and present landscape patterns in 25 sites. Two plant diversity measures were investigated; total species richness and species density. During the last 100 years grassland area and connectivity have been reduced by about 90%. Present-day habitat area was positively related to total species richness in both habitats. There was also a relationship to habitat area 50 years ago for continuously grazed grasslands. Only present management was related to species density: continuously grazed grasslands had the highest species density. There were no relationships between grassland connectivity, present or past, and any diversity measure. We conclude that landscape history is not directly important for present-day plant diversity patterns in ordinary landscapes, although past grassland management is a prerequisite for the grassland habitats that can be found there today. It is important that studies are conducted, not only in very diverse landscapes, but also in managed landscapes in order to assess the effects of fragmentation on species.
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| 35. |
- Cousins, Sara A. O., et al.
(författare)
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The influence of management history and habitat on plant species richness in a rural hemiboreal landscape, Sweden
- 2002
-
Ingår i: Landscape Ecology. - 0921-2973 .- 1572-9761. ; 17:6, s. 517-529
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Tidskriftsartikel (refereegranskat)abstract
- We explored patterns of plant species richness at different spatial scales in 14 habitats in a Swedish rural landscape. Effects of physical conditions, and relationships between species richness and management history reaching back to the 17 (th) century were examined, using old cadastral maps and aerial photographs. The most species-rich habitats were dry open semi- natural grasslands, midfield islets and road verges. Alpha diversity (species richness within sites) was highest in habitats on dry substrates (excluding bedrock with sparse pines) and beta diversity (species richness among sites) was highest in moist to wet habitats. Alpha and beta components of species richness tended to be inversely related among habitats with similar species richness. Management history influenced diversity patterns. Areas managed as grasslands in the 17 th and 18 th century harboured more species than areas outside the villages. We also found significant relationships between species richness and soil type. Silt proved to be the most species- rich topsoil (10- 20 cm) in addition to thin soils top of on green- or limestone bedrock. The variation in species richness due to local relief or form of the site also showed significant relationships, where flat surfaces had the highest number of species. In contrast, no significant relationship was found between species richness and aspect. Our study suggests that present- day diversity patterns are much influenced by management history, and that small habitat, e. g., road verges and midfield islets, are important for maintaining species richness.
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| 36. |
- Cousins, Sara, et al.
(författare)
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I nattviolens hage
- 2008
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Ingår i: Olsson, R. (red), Mångfaldsmarker. - Uppsala : Centrum för biologisk mångfald. - 9789189232297 ; , s. 9-28
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- I en svensk naturbetesmark kan man hitta över 40 växtarter inom en enda kvadratmeter. Det är världsrekord. En stor del av de arter som finns i betesmarkerna förekommer inte i andra naturtyper. Idag återstår inte mer än en tiondel av den areal naturbetesmarker som fanns i Sverige för drygt 100 år sedan. Igenväxningen hotar inte bara en lång rad arter. Också stora kulturhistoriska värden och vårt vackra, variationsrika odlingslandskap står på spel. Fortsatt hävd förutsätter att det finns en levande landsbygd med bärkraftiga jordbruksföretag.
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| 37. |
- Cousins, Sara, et al.
(författare)
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I nattviolens hage
- 2008
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Ingår i: Olsson, R. (red), Mångfaldsmarker. - Uppsala : Centrum för biologisk mångfald. ; , s. 9-28
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- I en svensk naturbetesmark kan man hitta över 40 växtarter inom en enda kvadratmeter. Det är världsrekord. En stor del av de arter som finns i betesmarkerna förekommer inte i andra naturtyper. Idag återstår inte mer än en tiondel av den areal naturbetesmarker som fanns i Sverige för drygt 100 år sedan. Igenväxningen hotar inte bara en lång rad arter. Också stora kulturhistoriska värden och vårt vackra, variationsrika odlingslandskap står på spel. Fortsatt hävd förutsätter att det finns en levande landsbygd med bärkraftiga jordbruksföretag.
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| 38. |
- Dahlgren, Johan Petter, 1978-
(författare)
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Linking plant population dynamics to the local environment and forest succession
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Linking environmental variation to population dynamics is necessary to understand and predict how the environment influences species abundances and distributions. I used demographic, environmental and trait data of forest herbs to study effects of spatial variation in environmental factors on populations as well as environmental change in terms of effects of forest succession on field layer plants. The results show that abundances of field layer species during forest succession are correlated with their functional traits; species with high specific leaf area increased more in abundance. I also found that soil nutrients affect vegetative and flowering phenology of the forest herb Actaea spicata. The effect of nutrients shows that a wider range of environmental factors than usually assumed can influence plant phenology. Moreover, local environmental factors affected also the demography of A. spicata through effects on vital rates. An abiotic factor, soil potassium affecting individual growth rate, was more important for population growth rate than seed predation, the most conspicuous biotic interaction in this system. Density independent changes in soil potassium during forest succession, and to a lesser extent plant population size dependent seed predation, were predicted to alter population growth rate, and thereby the abundance, of A. spicata over time. Because these environmental factors had effects on population projections, they can potentially influence the occupancy pattern of this species along successional gradients. I conclude that including deterministic, as opposed to stochastic, environmental change in demographic models enables assessments of the effects of processes such as succession, altered land-use, and climate change on population dynamics. Models explicitly incorporating environmental factors are useful for studying population dynamics in a realistic context, and to guide management of threatened species in changing environments.
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| 39. |
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| 40. |
- Dahlgren, Lars-Ove, 1946-, et al.
(författare)
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Gruppera mera?
- 1986
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Bok (övrigt vetenskapligt/konstnärligt)
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| 41. |
- Dahlgren, Lars-Ove, et al.
(författare)
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To be and to have a critical friend in medical teaching
- 2006
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Ingår i: Medical Education. - : Wiley. - 0308-0110 .- 1365-2923. ; 40:1, s. 72-78
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND In order to stimulate reflection and continuous professional development, a model of critical friends evaluating each other was introduced in medical education. OBJECTIVE To investigate whether the critical friend concept can serve as a pragmatic model for evaluation of medical teachers and as a fruitful tool for enhancing self-knowledge and professional development among medical educators. METHODS Three pairs of critical friends were formed, consisting of experienced medical teachers (n = 6) at the Karolinska Institutet. Each teacher was assigned to give 1 lecture and 1 seminar in his or her specific research or clinical field. The critical friend evaluated the performance in class, acting as an observer using a pre-formed protocol. The evaluation was communicated to the teacher during a 45-minute session within 48 hours after the teaching session. Each of the 6 teachers was criticised and gave criticism within the pair configurance. The outcome of the process was evaluated by an experimenter, not participating in the process, who performed a semistructured interview with each of the 6 teachers. RESULTS Each teacher had a different way of reflecting on teaching after the project than before and made changes in his or her way of teaching. We also noted that being a critical friend may be even more effective than having one. The majority of the feedback provided was positive and valuable. CONCLUSION To be and to have a critical friend is worth the extra workload. Therefore, the critical friend concept should be made part of regular teaching practice.
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| 42. |
- Dahlström, Anna, et al.
(författare)
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The History (1620-2003) of Land Use, People and Livestock, and the Relationship to Present Plant Species Diversity in a Rural Landscape in Sweden
- 2006
-
Ingår i: Environment and History. - : Brill. - 0967-3407 .- 1752-7023. ; 12, s. 191-212
-
Tidskriftsartikel (refereegranskat)abstract
- The traditional agriculture in Europe favoured numerous plant and animal species that are presently declining. Integrated studies based on various sources are needed in order to unravel the complex relationships between changing landscapes and biological diversity. The objectives of this study were to describe changes in land use during c. 350 years in a Swedish agricultural landscape in relation to changes in human population and livestock, and to analyse relationships between historical land use and present-day plant species diversity. There were only minor long-term changes in land use, population and livestock between 1640 and 1854 in the two studied hamlets, but detailed data 1620-41 showed a large short-term fluctuation in livestock numbers. After 1854 larger changes took place. Grasslands were cultivated and livestock composition changed. After 1932, livestock number decreased and most of the former grazed outland (areas located outside the fenced infields) turned into forest by natural succession. 7 per cent of the study area is still grazed semi-natural grassland. The highest plant species richness is today found on semi-natural grassland with a long continuity of grazing. The distribution of five target species suggests that previous land use still has an important effect today. The majority of their occurrences are remnant populations located in previous outland pastures which are today forests.
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| 43. |
- De Frenne, Pieter, et al.
(författare)
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Latitudinal gradients as natural laboratories to infer species' responses to temperature
- 2013
-
Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 101:3, s. 784-795
-
Forskningsöversikt (refereegranskat)abstract
- Macroclimatic variation along latitudinal gradients provides an excellent natural laboratory to investigate the role of temperature and the potential impacts of climate warming on terrestrial organisms. Here, we review the use of latitudinal gradients for ecological climate change research, in comparison with altitudinal gradients and experimental warming, and illustrate their use and caveats with a meta-analysis of latitudinal intraspecific variation in important life-history traits of vascular plants. We first provide an overview of latitudinal patterns in temperature and other abiotic and biotic environmental variables in terrestrial ecosystems. We then assess the latitudinal intraspecific variation present in five key life-history traits [plant height, specific leaf area (SLA), foliar nitrogen:phosphorus (N:P) stoichiometry, seed mass and root:shoot (R:S) ratio] in natural populations or common garden experiments across a total of 98 plant species. Intraspecific leaf N:P ratio and seed mass significantly decreased with latitude in natural populations. Conversely, the plant height decreased and SLA increased significantly with latitude of population origin in common garden experiments. However, less than a third of the investigated latitudinal transect studies also formally disentangled the effects of temperature from other environmental drivers which potentially hampers the translation from latitudinal effects into a temperature signal. Synthesis. Latitudinal gradients provide a methodological set-up to overcome the drawbacks of other observational and experimental warming methods. Our synthesis indicates that many life-history traits of plants vary with latitude but the translation of latitudinal clines into responses to temperature is a crucial step. Therefore, especially adaptive differentiation of populations and confounding environmental factors other than temperature need to be considered. More generally, integrated approaches of observational studies along temperature gradients, experimental methods and common garden experiments increasingly emerge as the way forward to further our understanding of species and community responses to climate warming.
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| 44. |
- De Frenne, Pieter, et al.
(författare)
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Microclimate moderates plant responses to macroclimate warming
- 2013
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 110:46, s. 18561-18565
-
Tidskriftsartikel (refereegranskat)abstract
- Recent global warming is acting across marine, freshwater, and terrestrial ecosystems to favor species adapted to warmer conditions and/or reduce the abundance of cold-adapted organisms (i.e., thermophilization of communities). Lack of community responses to increased temperature, however, has also been reported for several taxa and regions, suggesting that climatic lags may be frequent. Here we show that microclimatic effects brought about by forest canopy closure can buffer biotic responses to macroclimate warming, thus explaining an apparent climatic lag. Using data from 1,409 vegetation plots in European and North American temperate forests, each surveyed at least twice over an interval of 12-67 y, we document significant thermophilization of ground-layer plant communities. These changes reflect concurrent declines in species adapted to cooler conditions and increases in species adapted to warmer conditions. However, thermophilization, particularly the increase of warm-adapted species, is attenuated in forests whose canopies have become denser, probably reflecting cooler growing-season ground temperatures via increased shading. As standing stocks of trees have increased in many temperate forests in recent decades, local microclimatic effects may commonly be moderating the impacts of macroclimate warming on forest understories. Conversely, increases in harvesting woody biomass-e.g., for bioenergy-may open forest canopies and accelerate thermophilization of temperate forest biodiversity.
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| 45. |
- De Frenne, P, et al.
(författare)
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Significant effects of temperature on the reproductive output of the forest herb Anemone nemorosa L.
- 2010
-
Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 259:4, s. 809-817
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Tidskriftsartikel (refereegranskat)abstract
- Climate warming is already influencing plant migration in different parts of the world.Numerous modelshave been developed to forecast future plant distributions. Few studies, however, have investigated thepotential effect of warming on the reproductive output of plants. Understorey forest herbs in particular,have received little attention in the debate on climate change impacts.This study focuses on the effect of temperature on sexual reproductive output (number of seeds, seedmass, germination percentage and seedling mass) of Anemone nemorosa L., a model species for slowcolonizing herbaceous forest plants. We sampled seeds of A. nemorosa in populations along a 2400 kmlatitudinal gradient from northern France to northern Sweden during three growing seasons (2005, 2006and 2008). This study design allowed us to isolate the effects of accumulated temperature (GrowingDegree Hours; GDH) from latitude and the local abiotic and biotic environment. Germination and seedsowing trials were performed in incubators, a greenhouse and under field conditions in a forest. Finally,we disentangled correlations between the different reproductive traits of A. nemorosa along thelatitudinal gradient.We found a clear positive relationship between accumulated temperature and seed and seedlingtraits: reproductive output of A. nemorosa improved with increasing GDH along the latitudinal gradient.Seedmass and seedling mass, for instance, increased by 9.7% and 10.4%, respectively, for every 1000 8C hincrease in GDH.Wealso derived strong correlations between several seed and seedling traits both underfield conditions and in incubators. Our results indicate that seed mass, incubator-based germinationpercentage (Germ%Inc) and the output of germinable seeds (product of number of seeds and Germ%Incdivided by 100) from plants grown along a latitudinal gradient (i.e. at different temperature regimes)provide valuable proxies to parameterize key population processes in models.We conclude that (1) climate warming may have a pronounced positive impact on sexualreproduction of A. nemorosa and (2) climate models forecasting plant distributions would benefit fromincluding the temperature sensitivity of key seed traits and population processes.
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| 46. |
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| 47. |
- De Schuyter, Wim, et al.
(författare)
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Declining potential nectar production of the herb layer in temperate forests under global change
- 2024
-
Ingår i: Journal of Ecology. - 0022-0477 .- 1365-2745. ; 112:4, s. 832-847
-
Tidskriftsartikel (refereegranskat)abstract
- Wild pollinators are crucial for ecosystem functioning and human food production and often rely on floral resources provided by different (semi-) natural ecosystems for survival. Yet, the role of European forests, and especially the European forest herb layer, as a potential provider of floral resources for pollinators has scarcely been quantified.In this study, we measured the potential nectar production (PNP) of the forest herb layer using resurvey data across 3326 plots in temperate forests in Europe, with an average time interval of 41 years between both surveys in order to assess (i) the importance of the forest herb layer in providing nectar for wild pollinators, (ii) the intra-annual variation of PNP, (iii) the overall change in PNP between survey periods and (iv) the change in intra-annual variation of PNP between survey periods. The PNP estimates nectar availability based on the relative cover of different plant species in the forest herb layer. Although PNP overestimates actual nectar production, relative differences amongst plots provide a valid and informative way to analyse differences across time and space.Our results show that the forest herb layer has a large potential for providing nectar for wild pollinator communities, which is greatest in spring, with an average PNP of almost 16 g sugar/m2/year. However, this potential has drastically declined (mean plot-level decline >24%).Change in light availability, associated with shifts in canopy structure and canopy composition, is the key driver of temporal PNP changes.Synthesis. Our study shows that if management activities are carefully planned to sustain nectar-producing plant species for wild pollinators, European forest herb layers and European forests as a whole can play key roles in sustaining wild pollinator populations.
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| 48. |
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| 49. |
- Ding, Jihua, et al.
(författare)
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GIGANTEA-like genes control seasonal growth cessation in Populus
- 2018
-
Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 218:4, s. 1491-1503
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Tidskriftsartikel (refereegranskat)abstract
- Survival of trees growing in temperate zones requires cycling between active growth and dormancy. This involves growth cessation in the autumn triggered by a photoperiod shorter than the critical day length. Variations in GIGANTEA (GI)-like genes have been associated with phenology in a range of different tree species, but characterization of the functions of these genes in the process is still lacking. We describe the identification of the Populus orthologs of GI and their critical role in short-day-induced growth cessation. Using ectopic expression and silencing, gene expression analysis, protein interaction and chromatin immunoprecipitation experiments, we show that PttGIs are likely to act in a complex with PttFKF1s (FLAVIN-BINDING, KELCH REPEAT, F-BOX 1) and PttCDFs (CYCLING DOF FACTOR) to control the expression of PttFT2, the key gene regulating short-day-induced growth cessation in Populus. In contrast to Arabidopsis, in which the GI-CONSTANS (CO)-FLOWERING LOCUS T (FT) regulon is a crucial day-length sensor for flowering time, our study suggests that, in Populus, PttCO-independent regulation of PttFT2 by PttGI is more important in the photoperiodic control of growth cessation and bud set.
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- Do, Hai Thi, et al.
(författare)
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Nerve growth factor (NGF) and pro-NGF increase low-density lipoprotein (LDL) receptors in neuronal cells partly by different mechanisms : role of LDL in neurite outgrowth
- 2016
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Ingår i: Journal of Neurochemistry. - : WILEY. - 0022-3042 .- 1471-4159. ; 136:2, s. 306-315
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Tidskriftsartikel (refereegranskat)abstract
- Low-density lipoprotein receptors (LDLRs) mediate the uptake of lipoprotein particles into cells, as studied mainly in peripheral tissues. Here, we show that nerve growth factor (NGF) increases LDLR levels in PC6.3 cells and in cultured septal neurons from embryonic rat brain. Study of the mechanisms showed that NGF enhanced transcription of the LDLR gene, acting mainly via Tropomyosin receptor kinase A receptors. Simvastatin, a cholesterol-lowering drug, also increased the LDLR expression in PC6.3 cells. In addition, pro-NGF and pro-brain-derived neurotrophic factor, acting via the p75 neurotrophin receptor (p75NTR) also increased LDLRs. We further observed that Myosin Regulatory Light Chain-Interacting Protein/Inducible Degrader of the LDLR (Mylip/Idol) was down-regulated by pro-NGF, whereas the other LDLR regulator, proprotein convertase subtilisin kexin 9 (PCSK9) was not significantly changed. On the functional side, NGF and pro-NGF increased lipoprotein uptake by neuronal cells as shown using diacetyl-labeled LDL. The addition of serum-derived lipoprotein particles in conjunction with NGF or simvastatin enhanced neurite outgrowth. Collectively, these results show that NGF and simvastatin are able to stimulate lipoprotein uptake by neurons with a positive effect on neurite outgrowth. Increases in LDLRs and lipoprotein particles in neurons could play a functional role during brain development, in neuroregeneration and after brain injuries.
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